Well, while I was waiting for a used seat pan to come up for sale (at a reasonable price), I decided to practice with the little HF MIG welder my wife got me last Christmas.
I must say, it was addictive, and after a couple nights, I had my broken seat pan back together, and gusseted for added strength. The welds are pretty sloppy, but I am improving!
I sanded her down and gave her a fresh coat of paint before I reinstall. At the least, this will give me some time to look for a deal on a used seat.