Official Luthiers Forum!

Chris,
I got mine off of ebay for $50.00. There were about 53 pieces in the lot. They came off of an old (circa 1890's) piano, and most pieces measure about 4.0"x0.5", and are 0.035" thick.
Marty

Often you can get then for free if you are willing to dispose of the rest of the piano! If you can find an older piano (1700's -1850's) the key covers tend to be thicker. The key tops can be laminated with super glue for saddles.
If you don't want to deal with the legal issues you can buy nice looking mammoth ivory for not too much money. Since mammoth's at this point are not endangered species the ivory can be freely traded.