Hunt down an ATX power supply with the right dimensions (which will be a little challenging, since it is not the common ATX shape) and adapt it to the Mac. You'll need a couple of molex connector housings and pins and an inverter to convert the power on signal. I think instructions for the adaptation are on xlr8yourmac.com. They probably don't have an article about the 7200 specifically, but the 7500 uses the same power supply, and the 8500 uses the same pinout, with a differently boxed power supply.

But that way you can use a new power supply and not a used one whose components may be about to blow.

Of course, that may be too much work for a 7200/75... But if you build your adapter as a dongle, basing it on an ATX extender, which will plug into the supply end of any ATX supply, you'll never need to do another adaptation. Just plug in your adapter, install the ATX supply and go.