Don't know the machine, taking a shot here, and the auction may be over by the time you read this.

The 3600 rpm tells us, that the machine is probable a two pole alternator design. If this is true, then there would be a rectifier set for DC welding current.

As to the good stuff...Most of the parts replaced most often are usually not welder section parts, but engine parts. If the engine is or was in recent production, NAPA auto parts and others may be able to supply.

As far as welder section parts, the most often replaced parts are readily available from electric/electronics outlets. Rectifiers, switches, wire connections, relays, rheostats or potentiometers, welder studs, etc can be had from places like Newark Electronics, Allied Electronics, Graingers, Surplus Center and the like.

Actually, engine drive machines are usually less dependent on OEM (original equipment manufacture) parts than shop machines.

The only monkey wrench I can think of is the idle control, if there is one.
If not vacuum operated, there is a proprietary circuit board involved.
Hope is not lost. There are outfits like Innovat and others that will rebuild your board.

When buying used equipment-don't buy it,unless you can steal it.
You are often buying a pig in a poke. Which can often be ok if you can invest a little time and money in the project.

Good Luck
brande