Go to e-bay and put Dragonball anime cel in the 
search box, that should be a good start for you. 
There are also many good online shops to purchase 
from but that takes a bit of knowledge since many 
are in Japan and most only take IPMOs.
 Be forwarned: Dragonball is very hot and has 
been for awhile, good cels of those characters 
command high prices (good vegeta $200-$300 range)
You can find lower priced ones but expect a small 
image on the cel or partial features. Good luck