Good to see you're at your warhorse again, Stogierob. Rummaging through Google Image Search offerings for those few color photos of wartime Enfields, it seemed some had what look like regular black rubber handgrips while others had some sort of brownish material with what appear to be metal end caps. And then I stumbled upon this webpage, which I'm sure you're gonna love:
https://hollycat2000.jalbum.net/REMP2016/Personal/WD-CO/custom/index.html .
Here's a relevant excerpt:
"Early models were fitted with rubber handlebar grips, but later on in the war, rubber became scarce and canvas was used for the grips instead. Original canvas grips are very hard to find these days, so if you can't locate a pair on autojumble stands or via adverts, you can always have a go at making a set. They were originally made from a tube of Canvas but a good alternative is one of those old Army Side Packs, cut a piece of canvas and glue it to the handlebar or twistgrip. If you take care and make a butted joint with a razor blade, making sure it is at the bottom, you can't tell the difference. The biggest problem are the two rings on either end of the grip. A lot of these rings are made of Brass, but I've also seen plain metal ones. My brother is a plumber, so I managed to get some copper tubing that was a tight fit and it looks OK to me.
If you do find an original grip, bear it in mind that the WD/CO had 7/8" bars, other bikes like Norton used 1" diameter bars and you can also find 7/8" grips that are 6" long, so make sure you have the right size."
And here's an image from that article: