John, I got my tac off ebay, made in china. They gave me a full refund. Cost very little. Mine had a built in battery which I couldn't replace. It was clued in, soldered in. I tried to remove it and cracked the LCD. Junk at that point.
Here is one similar to the one I had. Only had to wrap the wire around spark plug wire. It worked great for just a few months then it got goofy because of dead battery.
I'll leave my email open if you want to chat more.