Speedometer question

[yetibone]

Hi folks!
I've installed porsche spindles on a '71 1302. As you all know any Beetle that is left hand drive runs it's speedometer cable to the left front spindle to be driven by the wheel bearing cap.
Porsche spindles do not have this provision. Does anyone make an electronic speedometer with a magnetic sensor and a reluctor wheel that mounts to one of the rear axles? (or any other means of keeping my girlfriend or myself out of a speeding ticket)



Gracias
yetibone