Though these machines have long been outmoded, there are still ways to source scarce items like parts, paper, tape, and ribbon. If all else fails, reach out to the venerable folks on GreenKeys-- between us all there are so many parts and accessories we could singlehandedly rebuild the teletype empire. People often post about stuff they'd like to get rid of for a nominal price or just for shipping. Sometimes folks are even able to pick up machines or supplies from a local sale and hold them until you can pick them up or ship them to you. It's a great group.
Obviously the estate sales of old hams/telecom guys can be treasure troves for these kinds of supplies, and it's better for them to go to a good home than to a dump, but you never know when these are going to occur nor if one will ever be in your vicinity.
Should you become aware of another good, steady source for any of these nonrenewables, please let me know so I can add it to this list.
Ribbon & Spools
Pretty much all of the old teletypes (WWII and earlier) used standard typewriter ribbon-- two inch spools, half-inch ribbon, eyelets at either end to trigger the ribbon autoreverse. Standard ribbons can easily be sourced from many places online. Most ribbons come on plastic spools nowadays, which is just sad to put into a heavy metal machine, so if possible you should try to source some metal spools and unwind the ribbon off of the plastic and rewind onto the good ol' metal spools.
<ebay & amazon source known for good quality>
Metal spools are usually very expensive to source these days due to all the typewriter hipsters flooding the world with terrible poetry. There are plenty available-- they're just expensive. However, I have sourced about 48 NOS metal spools from ebay for less than $2-$3 each with much patience and perseverance. They sometimes come up in lots of 12 or 24 for very cheap, and nobody else bids on them. This is probably because they're labeled as "teletype" or "teletypewriter" ribbon spools, so none of the typewriter hipsters know to find them. The NOS ribbon is usually too dry for use, though I have seen some very well sealed ribbon still work pretty well even after decades of storage.
If you have none, maybe source a couple at the gouge price and then lie in wait patiently to pounce on the good deal that will likely come again within the year.
There were two pretty standard types of paper teleprinters used through the years: friction feed and tractor feed. Friction feed is typically on a continuous roll, and traction feed is often fan-folded and has the lovely holes on either side. Both are similar widths.
While places like Amazon and eBay supply this kind of paper freshly manufactured, it's usually not a good deal. You can also find NOS canary stuff on eBay that looks really nice and authentic but is usually more expensive. There are a few good places to get newly manufactured stuff, but I have never seen anything new that's not white or offwhite-- nobody seems to manufacture the traditional canary color anymore.
<Cleanit supply> - Roll
<That other supplier> - Roll
https://www.labeloutfitters.com/search.asp?keyword=811-0-B55 - Tractor feed
<Paul Cembura NOS 3-ply carbon>
While printer paper has some inexpensive, newly manufactured options, oiled paper tape does not so much. I would imagine that manufacturing oiled paper is a more involved process, and as there are maybe a few hundred people worldwide who really want it nowadays, why would anyone go through the trouble?
11/16" and 1" oiled tape is probably most common; I understand the traditional "telegram" gummed tape was typically 1/4" and is virtually impossible to find, as are the machines that used them.
There seems to always be a source of NOS 11/16" paper tape on eBay for a case at a time. The price doesn't seem absolutely horrible-- around $6 or $7 per roll with shipping factored in-- but these rolls will go faster than the printer rolls, so it can add up. Once in a while someone will post a lot for much cheaper, so jump on those when you can.
<reliable ebay sources>
<aetherltd new source>
Teletype parts are a different world. Nobody manufactures them as it would be much too expensive to set up and machine accurately. 3D printing may be an option for some less impacted parts especially in later models that are minimally mechanical anyway, but many of these parts need to be extremely precise and hold up against constant wear in a way that plastic just couldn't handle. Some, such as springs, electrical contacts, and plugs may be replaceable with modern counterparts, but most are very unique.
The best place to source parts is from Paul Cembura, AKA Mr. RTTY, at RTTY Electronics. He literally has millions of Teletype Corp parts in stock in his warehouse in California for all models. He knows his stuff extremely well and charges reasonable prices. You need to supply the part number for each part you need, so you'll need to check the Teletype manual and find the needed part numbers, though I found that for certain types of parts, I was able to give him a description of what I needed explaining that I couldn't find a manual with a specific part number for it (for example, quarter inch jacks with the round "RED" "BLACK" label). There is a $20 minimum on orders. He'll probably even be able to offer tips on how you might solve a certain problem. If you're in town, he seems glad to accept visitors to his treasure trove, too.