Do you know that problem? Everytime you are in your workshop you suddenly need this one bit to adjust your tools. And of course you cannot find the bit driver.
Here is the solution - just put this tiny mini bit driver to your keychain and carry your most loved bit with you when you grab your workshop keys.

Print the top and bottom in PLA with a layer height of 0.2mm, 3 walls, 5 tops, 4 bottoms and 15% infill. Support is not necessary. I recommend using a brim, that will improve the bed adhesion.
The optional gasket should be printed in TPU. Use a smaller layer height (e.g. 0.12mm), no brim, 2 walls, 3 tops & bottoms, no infill and no support.

For assembly just add a standard bit. I testet serveral bits and they all had a tight fit. If necessary you can add a Ø5x2mm magnet - there is a hole for it inside the driver.
Screw the top part on the bottom part. The thread is similar to M12 but extra tight so It does not come open in your pocket. The gasket is optional and can help to prevent unintentional opening of the thread. If needed just press the gasket over the thread to the little groove at the bottom end of the thread.

Update
See my newest remix, the Mini Double Bit Driver Keychain: https://makerworld.com/de/models/36767#profileId-34998

Disclaimer:
This work by blecheimer is licensed under CC BY-NC-SA 4.0
You are not allowed to copy this model to other 3D printing websites without my permission.