40.5mm to 39mm step-down adapter?

[Stu W]

I just bought my first ltm camera, a IIIc. Everything I have is m mounts with 39mm filters. I bought an Industar 61 ld to start but the filter thread is 40.5mm. I can't seem to find a step down ring so I can use all my 39mm filters. Are they made? Thanks. Stu