Neat, I do believe that is the first time I've seen a Huey like that. As far as finding AM, that is probably pretty slim, but looking at the pontoons I think you could probably make something decent looking pretty easily. I'm thinking probably some styrene tubing and then either building up a frame for putty or a scupting epoxy, or as you said maybe balsa. The few helicopters I've seen like this seem to utilizize a lot of the regular landing gear, but you would need some better close ups. I recently finished an H-19 with pontoons and it used the rear legs of the landing gear almost unmodified, and replaced the front legs with a cross brace and some struts.
Here is a conventional H-19
and the H-19 with floats
It is hard to really tell from your photo, but it looks like they are just attached to or around the regular skids.