I've used those Bopla boxes. They're about €50 per part with custom milling and foil keypad for 50pcs.
The inside is tricky though, since you can assemble it straight or sloped. Whe sloped you can't have a pcb all the way trough since the battery compartment collides with your board.
Straight you'll have to use the rubber bumpers to cheat a few mm for a full length pcb that can actually contain some stuff.
Of you could just buy a larger one. They have 5 sizes iirc.
A bopla representative recently visited me and showed me their Bocube series, which is a nice twist to regular plastic boxes. Or aluminum for that matter.