The Hot Wheels Speed Driver shows on the package how it is designed to be used with bits, but there always seemed to me to be something missing: A way to hold the bit in place! Especially if you want to carry it around in your pocket.
I took an existing design on Thiniverse and modified it so it snaps in place and holds the bit securly. It has been riding around in my pocket for a week now without coming appart.
The bit is a 1/4 drive and 2" long. Here is the one I used: www.amazon.com/dp/B000RGW0C8
Interestingly, and quite disappointing, is that the newer castings (2021, green or red w/ silver wheels) had the chassis redesigned, and for some reason the 1/4 drive wont fit. It is less than 0.1mm smaller, but enough to make it unusable. I'm not sure if that was on purpose or not.
I've published the design on Thingiverse if you want to give it a go. Let me know what you think!