Casinos don't sell their obsolete chips like they do playing cards and dice.
Some quantities of old casino chips do make it out to the collector market, but not routine.

If you're located in Oregon, I suggest you attend the Casino Collectibles show to be held at the Chinook Winds Casino in Lincoln City, Oregon -- March 9 & 10.

Look for a Dean & Jodi (their business name is Casino Collectibles). They have had boxes of old casino chips for sale in the past. If Mike Spinetti is there, he might have box quantities too. Perhaps others. Even if you don't find them at the show, you might get some leads from the dealers in attendance.

Also, try the casino chips category on eBay. There are sets of chips sold there. A while ago, Mike Christiansen was selling quantities of obsolete Crystal Palace (California) chips, though I can't find any of his auctions right now. I don't have his email, but I recall he was located in Rancho Palos Verdes, CA.

Hope that helps.