This mini screwdriver has an inner compartment for you to store the bit - or to have a second bit, in case you decide to leave one always on.
Carry it with your keys or just leave it in your bag, it's always handy to have a screwdriver at arms reach.

I've found the fit to be perfect with the bits I have, but if you find the fit to be too tight or too loose, just let me know and I can upload more versions. I have also included a step, in case you want to make any changes.