[Shootist]

I have 2 of these lenses and a 39mm Leica filter does screw in part way and seems to fairly secure on both of them. As for a hood you could get a screw in 39mm and screw it into the filter.
The original hoods are almost impossible to get and I don't know of any aftermarket types that would screw into the threads of the 40C, at least no better then a 39mm filter does.