Making a battery tray isn't hard, if you have some basic power tools. One easy way to do it is to order some architectural channel from onlinemetals. I used the architectural channel because it has a nice neat 90 degree angle on the inside. I then split it in half so that I could widen it on the inside to accommodate the width of my packs. I then took a 1/8" thick X 2" wide piece of aluminum bar (from Home Depot) and put it into a vice and put a 90 degree bend in one end of it. I then mounts the two halves of the channel to the bar and used JB Weld to fill in the gap between the halves of channel. I used aluminum round bar to make stand offs and voila. You could also use something like nylon or delrin round bar to make the standoffs. It's easier to work and threads very well. It took me a couple of hours to do, but it came out nice and holds up to crashes very well.

If you prefer, you could use carbon fiber angle from graphite elegance instead of the aluminum channel. I did this on my truggy to keep weight down.