Of the pen kits that Elwin mentioned (all of which are PSI kits), I have made a lot of the Slimline Pro pens ( which uses 8 mm tubing ).
In particular, I like to make it as a single barrel click pen.
One thing I don't like about this click pen is that the click mechanism operation is a bit rough ....... AND noisy.
However, it does seem to be reliable.
By the way, I think that this design comes only as a click pen or as a pencil. . I have not seen a twist version.
I think, if you look, there are some other pen kits (that you might like and find appropriate) from other vendors like Berea.