Is there a way to post a pic in the forum messages? I couldn't find one.
Any way, the cartridge is 5 1/16" long. The ink tube is 4 1/2" long and slightly less than 1/4" dia. At the tip end on the tube is a flaired ring and taper 9/32" long. The ring is 1/4" dia. where it buts into the ink tube, then tapers down to the tip. The tip is 3/32" dia, x 3/8" long. The flared ring holds the refill in place, it's captured between the pen body and the pen tip. The pen body is 0.282" dia.x 5/32" long where the tip screws on. The threads are very fine, about 30tpi.
If I can't find a kit that can either be used directly or modified I plan on using a brass tube to reproduce the threaded end of the pen body but I'll have find some in the correct size and make a threading die for it. I would reuse the original pen tip, perhaps plating some in differant metals.