Any advice on where I could find a 59mm protective filter? I generally prefer to use filters when I take my lenses out on the street, or especially when traveling. So when I buy legacy lenses without filters, I try to pick one up right away. But ... I just picked up a beautiful Zeiss C/Y 135mm/f2.8 lens. I have too many 135mm lenses already, but I couldn't resist this one, and it's quickly become one of my favorites. But ... It has a 59mm filter thread! I've never heard of 59mm filter threads before, and apparently neither has eBay, Amazon, nor BH.