I think I saw someone mention they wanted some of 
these in a show me thread awhile back, and when I 
stumbled upon this site, I figured I may as well 
post it.  Now, I'm not sure if they're still for 
sale, seeing as how I'm on a cel hiatus and 
haven't emailed the owner myself, but it's worth 
a try.  Good luck:

http://www.legacy-
animation.com/production_cels/mlp/

Signing off,
Chaotic Serenity