http://www.rc-monster.com/rcm.php
for the mount, it's on the bottom. Reg. the tray, search the shop, at least losi has one; i have made it all myself, so I 'm not an expert for the tray. where do you live? in germany jamara has now a batt tray.
or you build it by yourself. there are many possiblilities, from cnc-drilled, to epoxy to thick lexan (which is a thermoplastic, like that easy to do), or even wooden ones. I have read about kydex, which seems to be ideal for that use (thermoplastic). to mount it you need some screws and some velcro. mike has some specific ones for that use, too (I think).
of course you could make a motor mount by your self, depending on your motivation and talent. mike#s mount has at least a lot of "bling-factor". mine has NO bling-factor, but works excellent. important thing is, it has to be stiff and solid.
flo