I put one on my 1809.
I unbolted the propane tank holder and moved it forward a couple inches, that gave me the extra room needed to fit the metal box in.
As you can see I have two batteries, and their is not much room in their for anything else. You would need a good solid partition to keep heavy metal items from bashing into the batteries and wiring.
I bought mine at Canadian Tire, but I've seen them at Princess Auto (up here in Canada) and other places online. I bought some square end U-bolts to hold the box to the trailer frame. I also put vents in the box, and a fuse and main battery kill switch.