I've been trying to source the additional parts for this and have come across a couple of interesting things.
One is a source for the high-current plug-unplug stuff that seems to be a bit cheaper than ordering from the manufacturer (esp. on shipping): https://www.scrubbercity.com/SearchResu ... 300&page=1
As far as protection, a lot of reviews of the cheap circuit breakers have complained about them tripping too low (or to high). So I'm thinking fuse. There are cheap ANL fuses like: https://www.amazon.com/InstallGear-Gaug ... op?ie=UTF8
... but I also came across this intriguing option at Mouser: https://www.mouser.com/datasheet/2/240/ ... 372356.pdf
About 32 cents, but they are "bolt down". So I guess you'd use some nylon bolts (or some kind of bushing on metal ones) and then thread metal nuts on top to contact the fuse. An "insulated standoff" like this perhaps: https://www.amazon.com/Baomain-Support- ... ay&sr=8-29