I have never made jewelry for the pets, but I used to make stuff for my friends for holidays and stuff..
One of my favorite places to buy from is
http://www.firemountaingems.com/
They will even send you catalogs... and their prices are pretty decent

And each month they have clearance stuff.... really cool
Like I said I have never made for the pets so I don't know what beads are best for pet jewelry, but there are tons to go through at fir mountain