I've never actually been able to find true cel-
making material on the common market around here; 
acrylics and acetate work well enough for my 
piddling. I would suggest though if you're 
serious to contact various in house animation 
production studios nearest you. They could 
probably point you in the right direction for 
good quality materials, but I doubt they'd be 
cheap.

G'luck in your search,
-Heather in Holland