As far as I know, POR-15 products are only available through certain distributors. If I recall I think Motor Sports carries it, but I think only specific products and not their whole line.
My point of contact is a guy named Chuck over here in Oregon.
His address / phone is:
Custom Product Sales
3115 Crocker Road
Eugene, Oregon 97404
(541) 345-8092
I'm sure he can either tell you whom to contact, or can sell you the stuff directly. I don't have any connection with him and I don't receive anything if you buy from him.
The Super Deluxe All Product Kit, is kinda spendy at $120 but it has EVERYTHING. Not only the products but also the brushes, gloves and safety breathing mask. They show a guy repairing a floor pan with it.
I have a neighbor up the street that has done both floor pans and repaired the removal of a spare tire well from his Datsun (510?), not sure of the model, the little boxy one. From what I've seen, it is amazingly STRONG stuff and surprisingly light. I'm still old school, so for me, floor pans should have new metal welded in, but having seen him sit and jump up and down on his floor pan after he's essentially FILLED A HOLE in the sheet metal, as well as removing his spare tire well and repairing the hole with this stuff, I'm impressed.
In my book, this stuff is great for what you're attempting, and from what they say, even more. Give Chuck a call, get a catalog and decide for yourself.