BIG STIRLING ENGINE RUNS ON ANY HEAT SOURCE - 850RPM 58cc - FULLY ASSEMBLED | eBay
I watched the video of it spinning a flywheel and have doubt that its 500 watts of power =/ Near the bottom of the auction he claims that if given the right conditions it can produce 500 watts 24 hours a day. That said its the biggest of the relatively cheap and currently produced stirlings I've seen as most are just toys or so well made they cost a fortune.