If it's completely painted, you're better off replacing it.
I seem to recall that someone sells Traynor style grille cloth, but I don't recall who.
Some Traynor photos...http://www.lynx.bc.ca/~jc/traynorAmps.html
Another idea: If the silver accents are on both sides of the grille cloth, could you remove it from the frame, reverse it and reinstall it?
Now you need the 1x18 folded horn with two 8 in. speakers in front to go along with it!