Signature plastics does make ALPS compatible keycaps, though I imagine the profile would be off a bit. Another option is to buy a broken Dell (AT101, AT102...), NeXT, etc. on ebay and pull the keycaps off it. I have some ALPS keycaps, I might be able to give you one, but it won't match the profile at all. I guess I could SELL you a full set of doubleshot ALPS keycaps from NeXT, for you to replace your A-Z keys with, but it wouldn't be free.
There are a lot of options, actually.
About the switch: It isn't glued in, I had the stem from a cheap ABS ALPS key break off in the switch. No idea how to get it out. I'm picking at it with a needle from time to time. ALPS keycaps sometimes fit very, very tightly. If you can get it out, then it's time to find a replacement keycap.