I use a throttle lock by BrakeAway (P/N 7CP05), which has a brake-handle release, in addition to a dedicated switch-off lever, in addition to a friction throttle release. Beautiful craftsmanship and engineering. Works perfectly once it's installed, but it's a real pain to install (at least it was for me – took well over an hour!). It's not a exactly a cruise control, but it's nice to be able to rest my right wrist on long rides.