When looking for parts, I try to bookmark newspaper classifieds that are close to my area. I.E., since I'm in central Okla., I'll watch the OKC, Tulsa, Wichita and DFW classifieds. The race circuits in your area should have some sort of classifieds available, also. (BJEC, TSCEC for me...)
My '01 220 quit pumping coolant, so I began looking for non-runners or parts. I came up with a 200 bottom end, supposedly in good shape. $300 and $45 shipping got it to my door. Looked to be OK, so I transplanted the top end to it, and switched them out. This all happened over the last month or so, last night was the first run up and down the street. I'll be running it in the Boars Head Enduro, this Sunday. If I DNF, ouch!