Battery powered led - lightweight

Hi everyone –
I’m working on a new project and need to put a light source inside a 2 1/2” cube. It needs to be battery powered as there can be no cords coming from it. It also needs to be as lightweight as possible as the whole thing needs to be suspended from a magnet. I think I have a plan but electrical pixies confuse me and I thought someone here might be able to confirm or correct my idea.

My plan was to wrap a small cylinder of foam rigid foam insulation with 12v led strips (less than 12”) and then use two 6v (Duracell 28a) batteries as the power source. These are small and very lightweight batteries. I’d hollow the cylinder and insert the batteries into the rigid foam. Still working on a design for the switch but haven’t got there yet. Any thoughts as to if this will work? Thanks.

-- No craft is very far from the line beyond which is magic. -- Lord Dunsany — Instagram @grailwoodworks