I'm going to have to second (third?) the 
suggestion of haunting Yahoo Japan auctions. 
That's where both my beauties came from (were my 
site not down due to server hacking, I'd show 
the latest off). And oh to have had the money 
for the Yuki and Shuuichi cels that were there 
recently. The other one I used to have I was 
lucky to get from a personal collector 
stateside. 

There's at least two sets of repros running 
around -- some from the OVA and some from the TV 
(Raxa has some of the latter set, which are hand-
painted).

As has been mentioned, the real thing's pretty 
darn pricy 'cause competition's stiff, and the 
amount of cels is limited.

A.