I ended up buying this because it was cheap ($16.71 with shipping) and seemed to be of the right dimensions.
It works quite well. Not only can I fit both Altair (Dell Mini9) and Nyx (Asus Eee 900), but also Illapa (OLPC). Granted, it's getting a little tight with the third machine in there, but still. With just Altair and Nyx, I could probably put their chargers in too. With just Altair, I'd also have room for Ptah (Kindle1) or its successor, or various other bits and bobs.
So, /so far/, and I've only just received it mind you, I'm pleased with this purchase.
Oh, that reminds me. I'm currently planning to buy a NeatDesk 698 scanner. $400 sheet-fed double-sided scanner with mac software. Anybody have a recommendation for something I'd like better? The sheet-fed and double-sided parts are important. So is the Mac part.