Not that I know of, I think all the jet-drives use 2 blades, besides that, graupner only makes one kind of the 29mm drive. I too thought of cutting down a propeller, personally I think thats what the impeller is anyway. The only thing is finding the right diameter, my best guess so far is a 40-42mm prop, but it's just a guess. One problem with a 4-blade, is availability. First you need to find a company that makes screw on props and then find a 4 blade performace prop, which I don't think theres many of.

The impeller has to be cut from from a surface prop and I don't know anyone that makes 4 blade. 3 blades can probably be found. Check the Graupner props, but like I said I think they only have 2 blade performance props. Octura might make a 3 blade, but I don't how to attach one since they use a drive-dog. The other problem with an Octura prop, is they're bronze, so cutting it down wont be easy. I dont mean to be pessimistic, but I've already looked into this a bit. I have decided a 3-blade would be best, since a 4-blade simply takes up too much volume in the pump. Again I don't know where to find a 3-blade for this, which was why I was trying to make one.