Hey Ty
I live in Corner Brook Newfoundland and also have trouble finding supplies around here. My local fabric store does'nt have ballistic nylon like I used in Vancouver so I bought some canvas from them. If I was going to use that to cover the SOF canoe I am currently building I would use an exterior latex paint..its more elastic than oil based so cracking is less likely and its more enviromently friendly,thats a good thing and you can clean your hands and brushes with water..also a good thing.
But I am a little hard on my stuff so Im a little worried about how well a canvas covered boat will like me, so today I started phoning around for a supplier of ballistic nylon here in Newfoundland. After a few calls I found a place in St. John's call United Sail that has ballistic nylon..and to my suprise cheaper than it is in Vancouver! They will ship to you,the guy told me Sameday courier is there all the time.
So i'll be ordering some from them..I would recomend a water based polyurethane like Varathane for sealing, just make sure you get an exterior not interior so it's U.V. stable. Again,being water based its nice an clean to work with :-)
I would also recomend, if you use nylon,after you put on your skin give it a good spray with water. As it dries you can watch it shrink and tighten.Leave it to dry for a few hours...or better overnight, and brush on your polyurethane.
Hope this helps...happy building and paddling dudes!!