The Spice series calculators used a battery pack that had two cells with a total of around 2.4 volts. The cells were very similar to AA batteries, just a couple of milimiters short. So, when the battery pack ended its life, many users had the temptation of putting two AA batteries. As these were a couple of milimiteres too long, the case cracked and the calculator contacts were broken.
You could find ready-made packages in eBay, but Ignacio Sánchez had a better idea: why not create an adaptor, so that normal (or rechargeable) AAA batteries can be used? As they are shorter, an adapter can be created where pressure to the contacts is moderate, and the battery cover can be closed without difficulty. So we went to the drawing board (actually Autodesk Fusion 3D) and off to the 3D printing company!
You can find the product here, and some pictures below: