Try asking for "door skins" explicitly at the the home improvement stores. That will probably get the clerks steering you towards the 1/8" luan. I built using the 1/4" luan, and have no complaints. Bending it for the hull was no problem, though trying to arch it over as the deck was a hard battle that I gave up on. For a deck I'd be much more inclined to go with 1/8"

Shop it around. Luan is not all the same. Not by a long shot. The stuff at the Home Depots around here is very good, with nearly uniform layers of inner fill and outer skins. The stuff at Lowes has tissue paper thin outer skins. Various lumber yards have various grades and qualities as well.

Epoxy isn't on every store shelf, as you've discovered. So it often involves shipping. People have been saying good things about Raka recently on this board. It's far cheaper, and might be worth trying if you really want to switch.