They can be purchased at the Gomorrah casino to be used for playing in this casino's games only. The games using these chips are slots, blackjack, and roulette.
The chips can be exchanged for bottle caps, Legion currency or NCR dollars with the cashier inside the Gomorrah. The Gomorrah casino is also the only place to exchange the Gomorrah casino chips for currency.
The only other situation allowing the player character to earn them is if the Courier tells Cachino they want to play some games after completing How Little We Know in his favor, for which he gives 50 chips.