I'll take a swing since nobody else piped up -

I think you can buy tubular aluminum from the larger hardware chains - not sure what tires you have, but make sure you get the right diameter. Don't forget the bearings, if your tires are supposed to have them. I have some older Cat Trax style, inflated wheels with no tread and the rod-style plastic bearings. These seem to work well on most surfaces for the Wave. I have the V-shaped carpeted cradles from Murray's on them. Once the boat is on and tied, easy for one person to balance and steer, but at 130 lbs., I need help getting up sandy dunes - how steep is your hill?

Got my trax used from a Wave owner that uses carts rather than trax - click here.

Good luck - let us know what you work out.