Two tips no one thinks about:

1 - Walk around outside the casino, and look for chips on the ground! Yes, people sometimes drop them or toss away an unlucky chip. Especially if the casino is in a remote area (like Indian ones). But be careful not to trespass on casino property. And don't try it at the Red Hawk Casino in Placerville, only casino in the world where patrons are NOT allowed to walk outside the building!

2 - Telephone the casino, and ask if they could send chips through the mail, obviously if you pre-pay for them and provide a return envelope. I was astonished one time to reach the Manager - turns out he was a collector, too, and he agreed to do this. (May not be legal in all states, but works in California.)