Filter for Bell and Howell regular 8mm camera?

I just bought a Bell & Howell "Two Twenty" regular 8mm camera and would like to use 100D film in it. However, it was originally designed for (I believe) 10 ASA and 40 ASA film, and the aperture will only go down to f16. I'd like to get a filter for it, so I can use faster film. But the lens is TINY. It's marked 10mm/f2.5 and the thread size seems to be 16-17mm or about 5/8". Anyone ever see a filter this small??

Thanks,

Pat Walsh

I have a new lens for that camera you can have