What a beautiful bike! Congratulations!
There is an
eBay seller in Massachusetts, I think ebay name is funthingsfound or something like that, who has original John Bull diamond grips for sale, and reproduction Britannia grips. The John Bulls are a rusty rubber color, the Britannias are black. I got the black ones.
I have a pair of Dunlop 26 x 1 1/4 tires that are basically sound. They must be 50 years old, but show very little wear, no cuts or tears. The tread is black, and the side wall is gum colored. The black part is in excellent condition, but the side walls have some kind of heat damage --left in a hot garage in the sun, I imagine. So they have a blistered, diseased look. Not pretty. I believe with the right solvent one could take that side wall rubber off, and replace it with something.... but I don't know.