hollowpoint,
As rick1970 suggested, go for Hella, Narva (or Anderson) sockets & a plug for your light.
If you put a socket in your quad & at a nice convenient place in your 4by, it will make swapping from 1 to the other that easy, & you'll get all the power to your spottie for it to work at its best efficiency.
Get enough of the high amp rated wire (preferably in red & black) to go from your batteries to your plugs, is by far the best way to wire up .
Please don't neglect fuses!!! A heavy duty in-line fuse, as close to the batteries positive pole as practical, is the best way to go, ( no offence meant coldchickens) to many vehicles have been lost to fire, due to neglecting to do wiring the right way.
I realize you can't go "down the corner store" where your living hollowpoint but i think there's a mail order mob in Perth, will try & find it.