Casinos commonly accept chips from other casinos in their area. Because a chip is a negotiable instrument at the casino of issue, each casino can return it and cash it in at the casino that issued it. The effort of redeeming the chips at the original casino is a small price to pay to allow a customer to use it to gamble at their own establishment instead of sending them back to the original casino.
Thus, casinos have what is referred to as a "foreign chip box" where they collect all the chips that they have accepted from other casinos. Periodically, they sort the box and return the chips and redeem them at the original casinos. Some casinos use runners while others use businesses that perform these services for casinos.
And yes, if you ask, and if you're lucky, a casino may allow you to peruse its foreign chip box and allow you to purchase the chips from them.