Just wanted to post this link for others looking for vintage-style grill cloth as the company doesn't seem widely known. I am in no way affiliated, just ordering some stuff from them.
They have a few Sunn-esque offerings:http://acousticalsolutions.com/product/acoustone-amplifier-grille-cloth/
If anyone in Europe is curious I have some samples I'm happy to pass on.
I've got samples of P8000, P3000, P2700, P2000, and P4540 which I'm ordering.