I'm one of the folks who's been collecting Dual 
cels. I hadn't noticed any on ebay, though I 
haven't looked there in a while...anyway, I have 
links to a bunch of sites that are/have been 
selling Dual cels on the page I linked to 
above...I don't know how well that'll help. 
Unfortunately, Animaxis was selling Dual cels 
(w/backgrounds) just a few days ago, but this week 
is Battle Athletes IIRC. Dual seems to end up on 
there about once a month, with about 15 cels at a 
time.

Alan Zabaro