Especially external ones with a USB connection!
But it's amazing what you can find on eBay. There's a nice Tatung Einstein (3-inch disks on that one) going at the moment, for instance. If it was a straight auction (rather than a "buy it now" deal) I might have been tempted to bung in a bid myself!
Also noticed a Dragon 32 in good shape (made in Wales, don't you know)! And an ACT Sirius 1. It's a pity that the medical equipment section isn't as vibrant
(good BS word, that).