I have a 500 that was radically modified by the PO who was an electrical/electronic engineer.
As well as completely digital speedo/rev counter and home made electronic ignition, he fitted a keyless ignition switch. Housed in a box below the r/h side panel, there was just one switch which you had to press in a certain code (at a certain speed) to switch on the ignition. I could never get the damned thing to switch on (off was easy!) so I replaced it with an aftermarket ignition switch (from
www.wemoto.com). The switch is the same for CG125 to Cb750!
As long as you switch the wires as per the original switch you can use anything and mount it anywhare.
Mine is located below the r/h sidecover as that's where all the wiring (for the old electronic switch) went. Now I ride around with a key hanging from there like an old Harley!