speters wrote:
I have an M-42 screw mount to EF bayonet adapter and there are many others. This one is and old cheapo, that I bought many years ago, I think it was somewhere in the 14 to 19 dollar range. But I have used it quite often and I never had any issues. I also have and old C-mount (srew) to EF bayonet adapter. One just has to google it and there should be a lot of options/offerings!
Found this with a simple search for bayonet adapters. There are many to choose from, this ones for Leica: https://www.cameraquest.com/adaptltm.htm and the screenshot is for Canon.