PVA can be insolubilized. The water-resistance of PVA films can be improved, but I don't have any information about improving acid resistance.
An internet search of "crosslink PVA" should provide other leads. Manufacturers of PVA emulsions may have some suggestions.
DuPont...
Try one of the structural foam panel manufacturers that sell laminated panels used in yacht hull construction
One is www.diabgroup.com
More information on this type of composite on www.boatdesign.net
Carol