www.hobbypeople.net sells several small nitro rc motors. I used these a few years back but replaced them with electric motors (and I saw more power, less noise, and less mess. In fact it was the beginning of my total conversion to electric.)

AP Hornet 0.09 R/C Engine with muffler $49.99
AP Wasp 0.061 R/C Engine with muffler $49.99

But get an E480 motor instead!!!!

Kurt