[ObjectVoice]

Found the revised link!:

http://www.justblair.co.uk/speakers/vintage-koss-pro4aa-restoration.html

 

[ObjectVoice]

Wow, yes, that degraded interior foam is truly horrible. Really oily & sticky and it refuses to get cleaned up...

 

[ROOMBAZOOM]

Well, I recently bought 2 non-working Koss Pro4aa second hand (around 15 euros) and they were totally taken apart when I got them... And with neither pads, nor drivers !!! Fortunately the parts were rather clean without dirty foam decomposing whatsoever. I had an Omenex KsK-dj150 with headband articulation broken on one side lying around so the idea to transplant these 50 mm 25 Ohm drivers into the Koss came to my mind.
Hard work to cut them out of their plate using a dented steak knife as a saw but these perfectly fit in the Koss driver housing site, with hot glue put on the black plastic surrounding to keep the driver securely stuck in its place(and also preventing leakage from sound frequencies in the free space around the edge).
See picts please for details:

Tested them with worn old earpads from a Philips Cityscape Uptown shl5905, they really sound terrific, hopefully close to their original sound signature but I do not really know for sure as I have no original drivers to compare with. Bass are ample and medium very present. Impactful sound indeed.
Asked a friend to get me new angled pleather pads on La Baie Électronique. Giving a monstruously big look to these cans and a slightly changed SS on voices I would say. A female jack base put with hot glue to fix it into the hole where the screw for microphone mount was and here's the result now:

Yeah, I thought some more detailed picts for the head-fiers lurking for the jack mod would be helpful:

This conveniently small piece of Jack perfectly fits into the hole(after a small cutting of the four edges of the front square) and comes from a 10$ supermarket headphone sold here in France (Hoé is the Brand name).

Thanks for watching, and I hope it will help.