I have the following filters for sale, which all fit the Cokin P-Series filter holder. They are all 84x120mm except the polarizer. The polarizer is what they call the P-Sprocket size. It is circular and slides into the Cokin holder.
The following are in near mint condition.
Singh-Ray Circular polarizer - $125
Singh-Ray ND-1 Stop - $50
Singh-Ray ND-2 Stop - $50
Singh-Ray ND-3 Stop - $50
Singh-Ray ND-4 Stop - $75
Singh-Ray ND-5 Stop - $75
Singh-Ray Galen Rowell ND-3G-SS - $50
Singh-Ray Galen Rowell ND-3G-HS - $50
The following two filters have very subtle marks/scuffs on the surface. I haven't noticed any adverse affects, but I priced them accordingly.
Singh-Ray Galen Rowell ND-2G-SS - $30
Singh-Ray Galen Rowell ND-2G-HS - $30