all you need is a soldering iron (of course) and a bike's brake's hose (I use it becouse I had it laying around and if you ant to buy it's cheap and also becouse it is metal inside, the tip is also metal and it's flexible and returns to it's original position to don't waste solder).
Step 1: Assembling
Make a cut in the handle to pass the hose.
Then hack the hose.
Cut it in way that it can be glued in the up part and that the tip gets near the soldering iron's tip. The down part is cut in way that the tip is at the same lenght as the soldering iron and leaves a space between the two parts.
To mount it glue the top part with hot glue and the down with tape.