I've decided to go ahead with one of these from Jaycar.
https://www.jaycar.com.au/battery-bo...plugs/p/HB8504
I opted for the version with more anderson plugs so that we have the option to use it also when camping on a site with no power, but I also had very little inclination to build myself a box. This is much more neatly presented for those with limited DIY skills IMHO
