Well I though is give the one off eBay a go. Copy/Paste this number into eBay search 251363717943.
Not the biggest capacity, but it certainly made good use of the small space available. Was very easy to install. Probably longest part was dropping and lifting the spare wheel!
Here's what was supplied. There was supposed to be some foam strips that were supposed to assist in keeping the brackets in place whilst installing. I think I tossed them in the bin by mistake though. Didn't make installation hard by any means. Instructions supplied are more than adequate.
The two white dots are the breathers. Almost looks like cotton wool. Not sure if they will end up getting clogged with dust. Time will tell. You might need to click on the image to see the breathers. My bad cropping
The mounting brackets line up perfectly with existing holes.
Hose adapter that screws into the tank comes with thread tape already applied.
I ended up using an irrigation right angle adapter (not supplied, but cheap from hardware) to get the outlet where I wanted on the tow bar. A few zip ties to lock it in position and job done!