Containing and mounting batteries, etc

Hi,

As detailed elsewhere, I am building an electric Trikke:



As pictured, the vehicle has attachments at the rear of the steering column head tube for a bottle cage. This is where I would prefer to mount my battery pack. The Trikke, however, can be folded for transit:



When folded, there is only about 5 inches worth of space between the swingarms.

I am looking for a case that could hold 3 x 12v9ah SLA's + controller + charger that could fit in this space. I prefer rigid cases to nylon, but perhaps I am being silly :: shrugs ::

Another idea I've had is to use an ammo can:



This would have to be mounted in front of the steering column head tube, if I wanted to be able to fold down the Trikke with it still attached. It would also give the Trikke a little too much of a macho, post-apocalyptic electro chariot look for my own personal tastes