Simple construction from 22mm copper pipe, two stop ends, a couple of springs, simple push switch, standard battery and a replacement e-cig connector.
Not too technical - a little soldering, three holes to be drilled, one nut, one rivet and some pipe cutting.
The connector can be soldered as shown or with the live center (red wire) only - recommended. This looks neater and is stronger but means you have to solder the connector into the hole in one of the end caps. I used a small butane torch to do this as it would take a more powerful soldering iron to heat the copper stop end. If you only have a soldering iron just make sure the hole is a snug fit and force the connector in as an interference fit.
I forgot to take the picture of the single wire version before soldering it into the end cap and tightening it - I will dismantle or make another at some stage and add the image.
Connect the center red wire to one side of the switch with a some spare length to allow you to fit the button.
Copper is fairly easy to work with. I drilled the holes for the rivet, switch and connector in a bench drill but these can be managed with a hand held drill. None of the positions are precise but it does help to make a mark first with a hammer and punch to start each hole.
To complete the circuit I soldered a small spring to the other connector of the push switch but anything that will not short against the body should make a connection to the live of the battery when it is pressed against it. Holding the switch from turning while I tightened its nut was the most tricky job as only one finger fitted...
Finally I coiled the excess wire from the switch to the vape connector into the tube and attached the stop end. I tightened both stop ends with tools to compress the olives initially, leaving the vapouriser end tight so it cannot be un-done by hand but loosening the battery end to allow removal of the battery for charging. Hand tight is fine at the battery end and creates a good connection to vape.