MR hilts typically have an ID of ~1.37". Chassis options are either 1" PVC (OD ~1.32") or grinding down some of the TCSS Graflex chassis discs (OD ~1.39").

I'd personally recommend the PVC route. SCH40 PVC has an ID ~1", while Class200 has an ID of ~1.18" A few wraps of tape around the pipe will give it a snug fit in the hilt. I'd recommend running a search for Madcow-styled PVC chassis. Enough room for an 18650, NBv2/v3, and the speaker just super-glues onto the end of the pipe. TCSS conversion kit takes care of the blade/LED holder.