Spence,
I have just made up a set of beach wheels for my mozzie. Got the cups from bendigo, axle was an old laser section, and plastic wheel barrow wheels I had to bore out a bit. A short length of PVC pipe either side of the wheels and some saddles to hold the tow bridle out and aluminum riveted it all together. Position on aft end of the dagger board case with bridle fwd to the dolphin striker and single rope aft for when you back up.
Just be careful how you secure it on your trailer, as if it can rotate and move it chews up the bottom of your boat. I drilled a hole through the axle and secure with a wing nut. This also means I can set it at an angle under the hulls to prevent stone chips when towing.