I'm surprised that no one has figured out that the material used in the Comm panels is just Grill Cloth. This material can be found on any "Fender" guitar amplifier of the day, and is still readily available. I have several Fender Twin Reverb's that have the same grill cloth as used in the Comm Panels. Have a looksie here at this link, midway down the page you can see the different styles:
http://www.ampwares.com/coverings.html
Bink
:lol Ok Fender I got my amps mixed up! :lol