High Planes do a contra-prop Mustang Reno Racer Carl, and in the past I have written to them asking if I could buy certain parts from their kits and have been able to do so. It might be worth a try.
Other than that, I have a set of just the Aeroclub Shackleton spinners only which I won't be using any time soon (I prefer the props they do but like the kit spinners better). Here's a pic of the High Planes spinner with Aeroclu props