[mikethedruid]

Fortunately C battery voltages are not high, so I just make my own using modern batteries. I solder the terminals together. Some liquid flux made from powdered violin rosin and rubbing alcohol helps with this. Make a suitable box from white cardboard, and there you are. The drain is so low that a series of C cells hooked up will last for years. You can also tap them off to get -3, -4.5, .-6, -9 volts, or whatever you need.