I've used one of these, because I find them to be the easiest way to get the ignition live I need, unless you know of a spare outlet in the fuse box.
Ring Automotive RBGDCHK 12V 24V 5A In Car Dash Camera Hard Wiring Kit Single | eBay
Ring Automotive RBGDCHK 12V 24V 5A In Car Dash Camera Hard Wiring Kit Single | eBay