I came over a thread last week on Apple Discussion forums talking about how to get cartridges to old apple printers, and the conclusion was that all these printers used cartridges that still exists today in other printers. Because Apple just white labeled their printers/cartridges, and most of these parts are mass produced.

They came up with a bunch of models that fit the printer they talked about, but I can't find the thread any more..

Some guys said that it works by taking the cartridge to a office depot and find one that fits/looks the same, or that some of staff may recognize models that work. I remember my dad picket up a new cartridge at a random office depot for the StyleWriter about 10? years ago, so it seems to work at least some places.

You could also try to fill it yourself: http://www.jagshouse.com/stylewriterink.html

Edit; I found a list at apple.com that describe what 3rd party ink cartridges that work with the Stylewriter