I know that you said "slot" glass, but only because of shape does one know it to be slot glass if the image shown does not call out the casino or pays. So, I am suggesting another glass (pinball machine back glass) for which pool and billiards has been a theme for many machines.

And, there is a Pinball Machine Museum in Las Vegas where the owner can be approached for back glass that depicts pool/billiards. Never can tell what you'll find there, maybe even some slot glass!

Jim