Whoowy, 219 bucks for the bushed rotary valve version.
https://www.mecoa.biz/shopdisplayproducts.asp?id=45
VT .21 SPECIFICATIONS Displacement .21 cu.in. (3.5ccm) Bore x Stroke 0.654 x 0.63 Power .35 hp RPM Range 2500 ~ 15,000 Weight 9.5 oz Prop Size 8x5; 8x6; 9x5; 10x4 Prop Nut Thread 1/4" x28
Check out the 25:
http://www.mecoa.com/hp/vt/25.htm?id=2115