The Pilot Hi-Tec-C is a gel-based pen that is very popular in Japan and is also a cult favorite among twenty-something and thirty-something computer geeks.
I've seen several pen kits that claim to use gel refills, but they all seem to have a click mechanism. One of the known characteristics of true gel pens is that they must be tightly capped when not in use to prevent the gel ink from drying out. The closest that I've seen to that is some roller-ball kits what have either a snap-cap or screw-cap design.
There have been at least three Kickstarter crowd-funded ventures to design bodies that will hold hi-tec-c refills - the most famous is the Pen Type A square-cross-section stainless steel pen that also doubles as a pocket rule. My son was an 'investor' in that venture, and the pen that he received in return is certainly clever, but not worth the $99 retail price (to me).
You might try adapting a roller-ball kit. Failing that, you could be facing a kitless challenge.
