12V/5V Cigg lighter/USB power

Hey All,
I installed an auxiliary power outlet on my handle bar for phone charging.
I wired it directly to the battery so that I could use it to charge devices while the bike's ignition was off (has inline fuse).

This works to power devices just fine, but last night I went to turn on the ignition and the battery was flat dead since I installed it a few weeks ago, despite nothing being connected to it. So it's drawing current when not it use.

I'd like to splice into another power/gound - Where would ya'll suggest? I tried connecting to the license plate light since the rear lights were replaced, but didn't give power.

Thanks!

I would use a switched ignition hot to prevent this IMO. I would test the plug or return it maybe. Will look at the wiring diagrams in a bit and see for a good location with lesser amp draw unless someone else will chime in.