I am looking at possibly doing the same for the LQ9 going into our project.
That battery tray looks sturdy but the price is over the top.
There's a company named Ballistic Fabrication I'm looking at for a battery holder. I used their weld on caliper brackets on the 14 bolt in our project. Turned out good. They make all kinds of stuff for rockcrawlers.
Battery boxes are very reasonable...Like $36
http://www.ballisticfabrication.com/...xes_c_174.html