Back when batteries were expensive and low-capacity, it was common to buy a “battery eliminator” that could substitute for common battery configurations. [David Watts] must remember those, because he decided to make an eliminator for all the CR2032 battery-driven gear he has. He got some brass blanks about the size of the battery, and you can see the results on the video below.
His first attempt seemed to work fairly well, a sandwich of two brass disks, each with a Velcro spacer and wires soldered on to connect to a power supply. The fake battery looks as though it might be a little thick, but it did work once the battery holder was persuaded to accept it.
There is a worry that the disks might touch each other or accidentally the other end of the circuit, but depending on the power supply’s protection a fuse in the line might be appropriate. This would be especially true were the faux battery to be used with anything expensive or important. We love to see people experiment with different solutions, though we might have been tempted to simply solder a connector to the board across the battery holder or after removing the holder completely.
You can still buy eliminators, although usually they are just wall transformers with selectable voltage and a bunch of barrel jacks. However, there are some made with common battery pack sizes and — of course — you could 3D print something like that, too. Just be careful if you roll your own — gear meant for battery use may not handle ripple on the power supply line very gracefully. Or, maybe just print a battery.