As discussed in the other thread I believe there is no body selling them and originals/NOS have long dissolved in the oil they were packaged with.
Since they are not visible have seen people make and shape open cell foam for this purpose
Agreed. Nobody is selling them. NPD did at one time (as stock number "9A496-1A", the one I have seems to have a package date code of 9144, 1991, 44th week?). In the "1966 Comet, Falcon, Fairlane and Mustang Shop Manual", section 20 pg 8, that details replacing the smog pump filter, there is no reference to any oil, in fact it states - "Be sure the parts are dry before installing them." I did have an original (or "service", it came with the smog system) and it "disintegrated" over time (don't we all). It was a dark gray, almost black, and it did have the Ford engineering part number in raised (or indented, I don't remember) on it. The service stock number (per "60-68 Ford Car Parts" - aka MPC) is "C6AZ-9A946-A".
Measurements of the NPD filter are: 1/2 in wall (aka thickness), 1 1/2 in ID, 2 1/2 in OD, 2 5/8 in H. It is an open cell foam. Based on the ID, the calculated length of a flat piece of foam would be 4 3/4 in long, and based on the OD, it would be 7 3/4 in long. Cut the long version first, fit it in the "can" and the perforated metal cylinder attached to the can cover, then "trim" as necessary. I would use 3M8008 sealer to join the end to make a cylindrical sleeve.
Jim