Stan, if you want to laminate it to something flat, stiff, and light, look at Wedi Board or one one its knockoffs. Wedi is a foamcore backer board used for tile and stone installations. It's relatively light, waterproof, and very stable. Both faces are smooth and it comes in 4x8x1/2" sheets, and I think it also comes in 3x5x1/2" sheets. Two 3x5s might be perfect for the map size, using a couple of wood strips across the back to hold them together and act as hanging strips. Wedi has a proprietary adhesive for gluing the stuff together, edge to edge.
