kit parts

Trying to find sources that sell the individual parts of a standard slimline pen kit. Working on a customer's request to have a special .5 mm pencil design, but have been unsuccessful so far. Specifically, need the "plunger guide" for slimline pen by itself. I don't want to rob an existing...

Is is possible to get the plastic threaded section os the Center Band Assembly. I was showing a friend the pen I made and he turned the cap on too tight and stripped the thread in the center band section. I was able to rob a replacement from another pen kit, but would like ot get a replacement...