You could just drill and countersink holes to use a battery hold down post from another car. I have a yokomo battery hold down for sale since I got rid of it and switched to tape... You gotta understand that in pan cars, they use tape to save any bit of weight they can, if they wanted to integrate some kind of battery strap, they would have by now, but tape is the best thing to use to keep the car light, and it works fine holding the batteries down.