I used to buy neoprene sheets from a local Goodyear store. Not that I'm having them cut for me, that person is getting the stock from McMaster-Carr (they have an online catalog). I also believe that Graingers carries it -- they have outlets in lots of cities as well has an online catalog.
1991 Plymouth Acclaim 3L V6.
1 dry cells with nineteen 6"x8" 316L ss plates, driven by constant current PWM set at 35 amps (13.3V at PWM). 28% KOH electrolyte. Total measured output 2.5 lpm. Mileage went from 18 to 26 mpg, all city driving (44% increase). EFIE set at .370 and I still need to play with ignition timing.