Yes I still have the original spring loaded button- I did the mod myself .
It's a bit tricky getting at the button in a hurry while still in gear....!!!
To do the mod, I used a regular spare pickup brush and spring in a short length of thin copper pipe with brass washer soldered on for a internal flange,sheathed with plastic tube and fibre washers each end for insulation, and brass washer with Stainless metal thread set-screw.
Must've had to drill out the spring seat from the body though..!!