do you need to run THOSE specific lights?
i would look into something the just runs off 18V lithium ion tool batteries. at least their fairly cheap, readily available. most people have already commited to a portable tool brand and normally have the batteries and chargers already.
this guy hooked up some LED strips to his Dewalt stuff but should be plenty of options if you run another brand, there are also plenty of 3d printed adapters to use different brand batteries with other tools
if you have your heart set on those specific lights can you can always buy a 18v battery to 12v cig lighter, though not cheap ($70)
Makita 18v Battery Adapter With 12v Lighter Socket - Etsy Australia