What you are after is pretty simple. It will just need one extra relay. You interrupt the feed you already have by routing it through the contact on the new relay. Then, you connect the coil (pickup) of the relay to a switched source that only energizes when the ignition or another lighting circuit is on. I'd pick a source that is only on when lighting is needed, then tap into it to power the relay. In fact, in your case, you need a supply that is 'dead' when you switch off your ignition. Depending on your electrical skill level, this is simple, but you need to decide when you want to be able to 'switch on' in order to choose a source. I'm just sketching the solution as I am only familiar with my 2009 wiring which would be simple to modify.
PS: I HOPE that the supply to your lights has a fuse very close to the battery or you are at risk. If not, fix that.
PPS: When adding a relay, you'll need a switched (+), and a (-). DON'T ground the negative to the frame. Rather tap off an existing Ground / Earth wire. They are usually black. Be careful, this can go wrong in a hurry if you are not careful. Ask a knowledgeable friend if you are not confident!