I have had some luck getting different colors from the waitress. She's got them and I usually offer $5 for three chips or something like that. If you are offering $4 each you could probably knock it out with one helpful beverage server.

I recently became aware that cocktail servers at a major strip property are often harvesting $1 roulettes and waiting for $5 players to come in when it is busy and cashing them at $5 instead of the $1 they were originally tipped. The threat the casino worries about from the player that removes the chips.