Welcome, always good to have another Sunni owner here!
There isn't any exact replacement telex available unless it actually came off another vintage amp. There is tolex available that is real close though, you can often see it listed on eBay, and the last I heard Conrad Sundholm still has some available.
There are numerous threads posted here about both tolex and grill cloth, if you do a little digging you will get a good education on just about every facet of vintage Sunn resto.
