In the following video (timestamped): https://youtu.be/rylbFnTgFI8?t=107, you can very briefly see a C shaped battery contact within the "cap" of the battery kit.
The benefit of this specific contact is that, it is both spring-y and allows connection via screwing.
However, I have been completely unable to find its name, both in battery contact guides and in sales websites. Does anybody know its name, or if it is even sold anywhere? If not, any alternatives that may be similar?