+2 on posting here in the Wanted section, even posting on Craigslist. It's amazing how many people have things they'll sell but just need to be asked.
When searching, (craigslist / ebay) be sure not to JUST use "trx250r".. Search 250r, honda 250r, trx 250r, along with trx250r as many label them different. Also search title and description because some may just put "Atv frame" in the title.