Foam is one of the worst materials when it comes to vintage devices. I experienced it again when I recently decided to spend some time using my HP-71B (more on this later on this year). The original carrying case has a foam-ish inner liner. As expected, it disintegrated into a sticky black powder over the decades. Since I really needed a carrying case, I looked around and found one by Guerrilla that has the perfect size (Hard Travel Case G1-CALCCASEGRN for the green model). Although it was designed for modern portrait calculators, the HP-71B fits snug! I’ve removed the various internal straps and flaps, and I even have some room left!