I’m not saying that this works at all casinos, but typically I approach empty baccarat or pai gow tables (wherever they take commission and use fracs) and say that I’m looking for some cheap souvenirs and ask to buy up to 20, as well as including a dealer tip.
You also may have some luck buying from the cage but that’s a different animal with fracs usually. The same strategy might work though.
Playing will also work, but sometimes that looks even more suspicious because typically once you get fracs you pay your commission with them. If you want a few then it’s fine, but once you get to about 10 the dealers tend to ask to color them up, even if you put them in your pocket every time you get them.