Not difficult to make, I had to do the ones on the Peerless, and I need to do one of the Warwick ones.
2 Parts... A length of suitable size U channel, or grind the top off a square one. Just a bit wider than the glass is thick, , and as long as the glass A strip of 1.2mm (or so) the same length and about 3" wide.
Roll one edge of the strip around a suitable size drill, so that it's a J section, and weld the two bits together U..>..J.
"fettle" it wih a blunt implement until the roller wheel runs easily up and down inside the J. Stick the glass into the U with polyurethane windscreen adhesive. Grease J section liberally.
Can't promise to have it done for the International, I'm probably going to have to move house across the next two weeks, and Warwick things are scattered across most of Suffolk at the moment.
The biggest problem that you will have is stripping the door down to fit it!
If the one that you have is completely shot, it might be possible to bodge the old one out and wriggle/gloo a new one in without removing the glass.
Stripping the doors down is a real pain if they've never been apart. The hinge bolts are BSF for a start, and most of the nuts and bolts are BA, apart from the steel self-tappers that will have become an integral part of the door, and need to be drilled out.
When it gets really frustrating, remind yourself that Warwick doors are much better than Phase 1's.