There are no other adapters sold i know of. The connectors pins etc. are available from mouser electronics and you can use 2-atx+5v wires to a new crimp pin in your adapter or one heavier gauge wire(16 or 14awg).Did you check all the main power supply and motherboard connectors for bad contact and discoloration from heat? Assuming the A4000 motherboards been recapped and the zorro cards you are using have been recapped(old Tantalum caps can short and draw excessive current). Also address the Cyberstorm PPC card, I just replaced caps on mine,they were physically leaking.
The fast slot can have bad contact with the accelerator also. i install metal standoffs instead of plastic pins to stop the accelerator from creeping out of the slot over time and heat cycles. Deoxit is good for cleaning slot connectors. to be loosing so much voltage on the 5v rail is not normal and something seems to be dragging it down.
