One of the best flash units for Minox cameras, if you like to use flash cubes (or if you find some :-)). They tend to be rather scarce; not entirely hens teeth, but scarce.
The B4/C4 flash (cube) adapter for Minox B was initially designed and used the Mallory PX825, cell battery. These are now extinct, because they contained mercury oxide.
Of course people needed batteries to replace this now extinct one, so several models were and are available on the market now. However, they may be scarce, but a good start on finding them should be here:
Models replacing the now extinct Mallory PX825
Type: Alkaline. Voltage: 1.5 V.
Diameter: 23.2 mm. Height: 6.1 mm.
Do not use any other voltage replacements; while these MAY fit the innards of your flash, chances are you’ll play dice with the unit. And more likely you’ll be on the losing side, I pretty much guarantee you.
You can find the battery here, last I checked they were still available, click on battery icons to go to the respective shops:
Copyright of these images go to the respective shops.