Cels Forum

I would suggest looking at Usagi's House for new cel postings.
There was a nice cel of Ranma-chan for $50 (Ranma-45f) recently.
And, I would, of course, always watch Animagna for new cels.
There have been many reasonably priced, nice cels in the past,
Shampoo included.  There is a $90 Shampoo at Anime Galaxy.
I don't know how "nice" it is, but it is a cel of Shampoo.

Of course, when it comes to Pandas, I think you'll have to talk to
Noriko.

Finally, as has been said here many times before,
go look at Chad Kawakami's Internet Guide to Anime Cels at
http://www-scf.usc.edu/~ckawakam/cels/ and cruise around.
It's always a good place to start any search.