I completed a rehab of an '82 Mark IV rig a couple of months ago. I replaced everything except the tolex. Some things I got directly from Peavey. Some items from Antique Electronic Supply, and the grill cloth from Parts Express. It is an identical match to the original.
https://www.parts-express.com Go to the right and put in part number 261-800. Looks like they are out of it at the moment, but expecting it in soon. Good luck.
