Well, I don't know how useful this is, but a bit 
ago I saw one cel of Tora on Asylum Anime's site. 
I know that I did see who wound up getting it, 
but I don't remember. (We're talking this was 
sometime end of last year or very beginning of 
this year. . .) But the lucky owner was someone 
who does or used to frequent this Forum.

I also saw one on Yahoo Japan a *LONG* time ago. 
(Beginning of last year?) I have no idea who got 
that one - I haven't seen it since.

In any case, both cels were expensive. I think I 
remember the one on Asylum's site being in the 
$200 range. You might try writing privately to 
some of the bigger dealers - or possibly to Anime 
Link. I've never bought anything from Anime Link 
myself, but I know people who have and Link has 
turned up some incredible stuff in the past that 
I would have never imagined seeing in the US. O_O

Hope that helps. ^_^

Many Sharp Smiles,
--Drac