Where are you located?
On the EX500 mailing list there are a couple race bikes for sale. I was planning on selling mine too, but I knocked a hole through the cylinder head on the last weekend. Now I'm parting it out instead. :(
If you do get an EX500 I highly recommend you join the mailing list. There are plenty of helpful racers and non-racers there. Shoot me a private message and I'll send you the instructions for joining.
If you want to buy a complete EX racebike that just needs a new cylinder head let me know! ;)