I 3D print my own handles (and have the Gyrokey 3D models available on MyMinifactory. For the actual toolbits, I initially used Bahco bits and especially the grippy Torx bits were great (solid fit on screw heads), but they do corrode in use. So lately, I have switched to using Wera stainless steel bits and I love them. The bits are held in place with M6 stainless steel grub screws, so the assembly is a combination of plastic and stainless steel, which means that corrosion is a non-issue.
So, a very warm recommendation for the stainless Wera bits. I have bought them from Amazon and eBay. eBay prices were way lower than Amazon. They do cost a lot more than regular bits, but unless you lose the bit somehow, you're not going to need to replace it (probably ever).
A local shop that is considering offering my tools suggested I make some changes to the Gyrokey to make them fit better with masts that have very wide bases (like SABFoil), so there are some updates coming soon to those models and at least one new tool that fits much better into a small pocket and has two tool bits, so you can use it for M6 and M8 screws without changing tools.Here's my "marketing video" for the original version of the Gyrokey (single tool version - there's also a two-sided version that fits two different tool bits):