In my Graupner catalog from '98 (the 47FS) there is a 37.4 cc (2.28 ci) wankel with recoil starter listed...

It is rated at 4.9 hp at 10000 rpm. There is an optional cooling fan available for quote: " ...applications where the engine serves in a cowled situation and the high power output is fully used..."

The engine weighs 2210 grams (4.87 lb)

It is not an OS engine, and I don't know where the engine is produced.

It looks pretty compact for a 5 hp engine.

I have never seen one though...

The man who wrote this page seems to be pretty content about his 5 cc OS wankel... after he has rebuilt it to closer clearances and tolerances. He worked on the rotating piston body and the seals. According to him the tolerances and the surface finish of the rotating body are poor, resulting in poor starting behaviour and poor power output... He claims his engine puts out close to 2 hp at 20000 rpm. I'd love to see that... But I can also imagine that an engine like this has to be manufactured to very close tolerances to work properly.
OS Wankel report