Foams are gone huh? I hate how they disintegrate before the tires are used up. I've mostly given up on the supplied open cell foam, and either make my own, or I buy the blue closed cell foam inserts. The blue foams last as long as the tires.
Have you ever replaced the foam in a still good tire? It's pretty easy. Using a good X-acto blade, cut the inner bead of the tire around the rim. Fold the tire back on itself and remove the old foam. Pop in a new foam, then fold the tire back into place. Hand roll the tire a few times to seat the foam, then re-glue the inner bead. Now you can use up the rest of the tire.