Thanks for your input all...I just ordered some 3/4" white minicell T200 EVA from here:
https://www.foambymail.com/closed-cell-foams.html
They have a lot of options, thorough descriptions, spec sheets linked, and their prices are better (much better in some cases) than several other online foam-centric suppliers I found.
I've seen the padded hiking shorts, thanks, but I don't want yet another highly specialized clothing item, I just want to wear whatever suits the day & season, which may range from shorts in summer to wetsuit in the "off-season."
FWIW the throwable flotation device requirement is only for boats over 16 ft. (and also makes no sense for a boat with only one person in it...if I fall overboard, who's going to throw it to me?). I have actually been using those for butt cushions on my Montgomery 17 cockpit benches. They're too bulky for dinghy use, I want something slimmer that I can attach to the deck as I'll be scooting around to trim the boat and hike out etc. Along with the above for my Sunfish I also ordered some 1 1/2" EVA from the same source to make some proper seat cushions for the M17.
