Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

IIRC Sweden has done much in the fields of Stirling development over many years.

I think Ford Motor Company worked off of some Swedish designs to develop a nearly practical, or at least powerful enough to be usable, automobile engine.

These more powerful Stirling Cycle engines rely on entirely closed systems of "exotic" gases, that work at very high pressures that are not something that could typically or easily be maintained by the average citizen out in the real world.