I went to my friendly neighborhood Princess Auto today and after buying a bunch of tools, I found this. They do not normally sell the battery as a single one like YHR found, but have it listed as two connected in parallel with a harness and buzzer for $14.91. Of course, anyone familiar with PA know that their surplus area (which the batteries are found) is always changing. I did take pics for you all, including the part number for the two pack. Physical dimensions are: 6x3 5/8x1 1/4", weight is around 2 1/2 - 3 lbs per unit. The connections for the battery terminals are standard blade connectors. The double battery pack is 2 3/4" wide. I'm going to try and stuff the double pack in my Sherman- lower voltage will be easier on the drivetrain and the extra weight should make for great traction!

Oh, and each battery is 7Ah, or in other words will supply one amp for 7 hours. As my stock motors for my tiger pull at slowest speed (the highest amperage) a mere 0.15 amps, this means that I can run for 23.3 hours constantly (in theory). That is 7A/(2x0.15A). In real life, this is an all day battle battery. My only concern is if the batterys can be run on their side- otherwise they will not fit in a HL at 3 5/8" tall.