I have a great paddle key for home but I didnt want to trust it lasting long while mobile / portable / camping etc etc. So I did up the following. It has worked out quite well and I made 20 contacts the first day it was constructed.
Pictured below is the knee brace bottom which allows you to easily attach the paddles to your leg, but I have a normal bottom model done up as well
I played around with a few designs to get the paddles to return to normal but it turns out the simplest solution was a pen spring. I made a little notch that the spring recessed into. To keep it in place in case you add a drop of crazy glue to the indentation.
what I used for assembly....
3 x #6 1" bolts for the base
2 x #6 1/2" for contacts in the paddles
3 x #6 ring connectors to connect to audio jack
11 x #6 nuts
4 x #4 1/2" to attach top to base