I have two 77mm filters for sale from my old Canon 24-105mm lens. I sold the lens, so I no longer need the filters. Both are in excellent condition with no marks anywhere on the glass. They were both purchased new in May and used sparingly over the summer/fall.
Hoya Alpha 77mm CPL. $40 shipped, or will trade for a similar 72mm filter. Here's a link to the exact filter:
B+W F-Pro 77mm 0.6 4x ND filter. $35 shipped.
PM if interested.