Here is my controller/display (kind of archaic now, been in the car 7 yrs):
The mini toggle has an LED tip (hard to see in pic), lights up grn for veg and red for diesel. requires soldering in a resistor.
An adjustable (01-120 sec) time delay relay controls automatic purge cycle.
Personally, I like the simplicity of analog devices, but I do also like the copilot digital controller, probably would have gone this way but they did not exist at the time.
Rocker switches were for originally for electric heaters, but I have since ditched them since i do not find them necessary and dislike using electric heat for WVO.
Now I use the switches/relays for fog lights and front aux fan.
Car also has a 120V circ pump that works with blockheater, but the pump does not seem to do much unfortunately. I really want an Espar for this car since I drive it on veg year round.
The LED tipped toggle avaialbel from McmasterCarr
GL