Strapping tape.
Yes, it would work. (however being a little bit of a hassle) you may have to cut your tape in 1/2 in order to fit it through the slots.
It's amazing how expensive this sport is. Seems somewhat bottomless at times. Getting the sidebyside packs will also let the batteries sit lower in the chassis giving it better cornering (due to lower C of G) <Center of Gravity> There are a number of matchers that are on these forums that have good products for fair $$. I've used both promatch and fusion. They have both been worth the $$.