Locke, you will quite simply have to search through the sites that provide free games with embed codes for forums. And I am far from sure that there are any that come up in pop-ups...
But even if you can find such games, I'm still not sure that it would be such a good idea, looking at the fact that many of your members will have pop-up blockers of different kinds activated, not least as there are pop-ups from the advertisements on the forums.
About your URL, put it in your signature, and it will show up automatically with every question.
FoxLeonard