"Mine has begun to have a small hole form at one of the cross-folds, and I want to replace it"
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I just made a carrying case for my maps so they can stay unfolded.
Its a little bulky, but frankly when Im playing a game at someone elses place Im already lugging around a lot of crap and these maps are SOO worth keeping in mint condition, so its worth any amount of trouble to keep them flat and in perfect shape.
I just used two sheets of 1/4" plywood cut a little longer than the maps, then used Gorilla Tape for the folding hinge on the bottom. Works really great for carrying them around unfolded and great for storage.