Years ago I had the same problem and somewhere I read that you can mount a pickup truck starter solenoid down under the motor by the foot peg. I'll have to dig through some old paper work to find out the exact model but it did work well after I got the right length battery cable to run up to the battery. This solenoid was nice and big, not small like the OEM.
I now have GPS so I no longer get lost, just confused.
Retired and Loving it.
1975 Blue/ Green (Now Black) My main ride
1975 Red Gone to my son! (Burned Feb 2013)
1979 Black (to be restored)
1979 Blue (Sold)
1978 Black (back in the fold)
1993 blue 1500 Sold