For those who can get by with 100 W - I've got a box of very small ATX autorange PSUs (some call them µATX but that form factor doesn't actually exist) that probably fit into the original PSU easily. Yours for the postage.
100 W may not sound much but for a more-or-less stock machine it's enough. (I've been running 2 GHz Northwood P4 machines on those.)
I think they're SFX size, I can get the exact dimensions tomorrow.
