Lexan is so expensive you'll probably be the first to use it, but if you have some it should make a nice set of struts. Be sure to use spreader bars between the floats to keep them from "dancing". Unlike wheels or skis, float mounting should be as rigid as possible.
If forming the lexan doesn't work out, traditional wire mounting can be assembled from bent pieces. For a half-A plane, you could use 1/16 or 3/32 wire.