The easiest thing is just to search specifically for looping music. Most music made for games will loop, and you can find commercial use ones around in places like OpenGameArt.org
Or if you wanted to keep that piece to fit with your theme, you'd need to edit it in something like Audacity. There's a few tutorials around showing you what to do, but I can't really offer any advice since it's not my area.
He was definitely twisted. You guys have quite the imagination ;)
P.s. If you haven't seen it- just1witness made a let's play video of your game :D