This is designed to sit in the center of the handlebars. It is designed for inner tube to be glued to the feet and then to be zip tied to the bars. I do this for the cameras on my track car with great no movement results. The designed bars are 31 mm diameter
Drok Multimeter http://www.amazon.com/Multimeter-6-5-100V-Amperage-Backlight-Measuring/dp/B017FSED9I?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
On / off switch http://www.amazon.com/BQLZR-Latching-Self-locking-Button-Switch/dp/B00JQ5YS1W/ref=sr_1_101?s=hi&ie=UTF8&qid=1460129295&sr=1-101&keywords=push+on+off+switch+12mm These switches are generally sold as momentary (which you do not want) and you are looking for the latching version.
You will also need a 65mm x 44.5mm piece of Lexan. The Lexan needs to be 0.093' thick and I can buy it all day at the hardware store down the street.. Glue the inner tube to the feet, silicone the Lexan to the inside of the case, place some lithium grease in the cap of the push button and put together and wire up
Case is currently being tested 4-8-2016