Hi, Cecilia--
That's a good question. I've never tried a generic part with mine, although a high-shank generic roller foot showed up in a box of vintage attachments I bought several months ago. For what it's worth, my Meister came with a Greist #7 Buttonholer attachment which works just fine. That attachment is for a high bar (shank) - left needle position zigzag machine. I don't know how compatible it is with other machines since Meister 101s are rather uncommon.
As far as buying them, I bought two off eBay last year. Both were fixer-uppers. The first one cost me about $100 and I got the second one, which was in really rough shape, for under $80 total. I would see if it is at all possible to test-drive the machine. If it doesn't have a motor or light, both should be pretty easy to replace with generics. I would also look at the condition of the paint. If the paint feels rough and is cracked/crazed, the top coat is probably gone and you'd have to repaint it. If the nickel-plated parts are pitted, they should probably be re-plated. Take a good look at the needle plate to see if the needle opening is "bitten" which would indicate that the needle has come in contact with it and potentially damaged the bobbin case (which is a fairly generic part). Evaluate what you might have to put into it to get it running again: cleaning, servicing, new cords, new motor (1 amp), plus any parts which might be missing (bobbin case, etc.), new light. My experience is that it's tough to destroy these old war horses, but it sometimes takes time and more money to bring them back. The first one I bought off eBay had been sitting in a damp Florida basement for years, but my repair guy got it up and running without much trouble.
If you can get this machine for about $50 or less, it could be worth it. They are great machines. Let me know how it goes and if you want any more info about the Meister machines (history, etc.) let me know.
good luck!