Had the same problem, ended up making my own out of foam
with carbon fiber tube inserts for stiffness. 3/8" Carbon Fiber tubing from Aerospace Composite Products.
Do a search for Hirobo Conversion by P901 or threads by P901 and you can see the floats.
(Also on wattflyer with a bit more detail)
The floats are about 4" in diameter, 18 inches long and weigh 494 grams with a couple coats of water based grey spray paint, no fiberglas coating just paint over foam.
Pretty darn durable, many hard landings on water and in my stone driveway, never flipped over, (these things work much better than training gear ! )
Of course without any fiberglas on the bottoms I`m getting some dimples from the stones but my next move is to smooth out the bottoms with some lightweight spackle and then do a covering of the reinforced packing tape, should provide a tough lightweight solution.
Floats were fabbed, roughed out and finished in about 6 hours.
Scaled from an online photo of a Schweizer with floats.
Get the floats and the brackets made up and then float the whole thing in the pool (or bathtub in my case)slide the heli with brackets attached back and forth on the floats until you find the center of buoyancy where the rotor main mast is perfectly vertical, make a mark and thats where to attach the bracket to the floats !
Two strips of 6061 T6 aluminum make up the brackets that attach to the heli in the original locations so no modifications to the original frame. Takes maybe two minutes to change from skids to floats. The difference in weight between skid and float gear is a couple hundred grams, maybe 4-5 oz. so quite a benefit with not a lot of penalty.
Hope this helps, andrew