Richard,
I owned this engine and owned this prop: Graupner 16x8 3-blade. It will swing it at around 9000 rpm -> perfect match. This is the same load as Pro Zinger 18x6. You can get this prop from
www.hobby-lobby.com or
www.prop-shop.com
Master airscrew 16x8 3-blade will work too.
I also have the MA 14x7 3-blade, 15x7 3-blade, Graupner 14x7 3-blade & 15x8 3-blade. They are all for smaller engines.