The commercial pen kits are mostly ball points, with a few roller balls and fountain pens thrown in. I've never seen a kit for the kind of pen you are interested in.
But there are kitless option. There are a number of threads here about redressing Pentel mechanical pencils (0.3, 0.5 or 0.7mm) They are not difficult to do - an exercise in precise machining.
There are also threads on turning wood or plastic shells for Sharpie refills. They are a little more tricky because you need a special tap to match the odd thread on the refills.
I've never seen Copic pens, but the advertisements suggest that they are metal bodies that hold replaceable ink cartridges. So it shouldn't be impossible to do something similar to the Sharpie approach.