I bought a cheapo at Wally World that works OK for what I need. It works on my 6V 38 too which surprised me. It isn't as bright but it does the job. Clamp the sensing lead to #1 plug wire & hook the other two to the battery cable & ground.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.