Check out this geeky water powered calculator. It uses three water batteries for power that have two electrodes inside made from a special alloy which when immersed in water produce electricity through a chemical reaction.
Simply refill the batteries as the water evaporates, which is typically every 2 to 3 months and your calculator will keep crunching numbers and you’ll have no worries about harming the environment with dead batteries.
The water powered calculator is available to purchase for $11 from the Perpetual Kid website
Measures 2 inches tall x 5.25 inches long x 3 inches wide