Battery tray blues

While fixing some stuff to get the 5 running, I decided to remove the battery tray to clean it up and put some paint on the firewall to slow the rust down a bit. Surprise, surprise, the heads of the strut bolts in the firewall just twisted off. I intend to remove the fender to perform good repairs, but wanted to find out in the meantime if there is a good alternative battery tray available. Anyone have any suggestions? Pics of mods to get rid of the struts maybe?