You might try a rotating head from a Marx beacon. I don't know how (or if) they differ in construction materials from a Lionel equivalent, but my old Marx beacon would not only rotate, it would rotate so fast that it looked more like a strobe than a rotary beacon.
I do recommend the #494 beacon, though, as others have. I have my 494 on a variable voltage source, so I can fine-tune the amount of power and the speed of spin.