Brodak Maufacturing sells a very nicly machined aluminum spinner. I have one in front of me now. It came with a collar for the prop nut. The projection on the prop side of the prop nut is about 5.5 mm in diameter, with the adapter collar it allows the use of a prop with an 8 mm hole in it. I have a dial vernier caliper and in inches the dimensions are: prop nut .236" and with the adapter collar it's .314". Now if I can get this 1" spinner to work on a Cox .049 prop and hub you should have no problem. I actually had to drill out the Cox prop hub to a depth of 1/8" with a 15/64" drill bit. The spinners aren't cheap however, $15.00, but I think worth it.

Good luck,
Bill