Could you post a photograph of your camper, or maybe a link to one that looks like yours? Does it have a double-hull, like a Burro? (Otherwise I can't imagine how the fiberglass batting type of insulation is used).
I realize you aren't necessarily looking to replace like with like, in terms of the insulation, but I think it will help people to give suggestions if they can get a look-see.
Plus I've never seen a Vanguard and there are no photographs of one on the home page -- are you sure it's molded fiberglass (the camper, not the insulation)

Raya