Here is a working power supply I pulled from a Compaq Prolinea 5100 with a 100 MHz Pentium processor. Compaq used this same power supply for their Prolinea 575 and 590 desktop PCs, as well as their Deskpro 575, 590, and 5100
Compaq's Series PS2021 power supply is model CPS-148A with part numbers 213928-001 and 213929-001.
This is neither an AT nor a standard ATX power supply., Instead of a two-row 20-pin ATX connector to the motherboard, it uses two single-row connectors, of 8 pins and 9 pins. There is a two-wire cable ending in two small lugs which connect to the back of the power switch at the case front. The other four cables provide three 4-pin Molex power leads plus one small 4-pin floppy drive power lead.
I offer a 30 day return privilege (although return shipping is at the buyer's expense). Ground shipping is free to any U.S. zip code.