With an engine removed from the bike and no way to hear it running any second hand motor on ebay will not make big bucks as its too much of a buyer risk.. I was looking this time last year and was a fair few for 700 - 1000 listed as good working motors. You can make the guy a cheeky offer which is what I did.
There is BDMBoys breaker on ebay with what looks like a good engine for £999. Offers a 14 day warranty, though you cant ring him and he doesnt call you back when you leave a message. I offered £850 and he declined, probably best............ BSD have removed the engine and its on the bench waiting to be opened up so I'll find out the extent of the damage soon.