I quite liked the idea of darthskids Snap in battery tray for Eachine Aurora 90, but it didn't fit my batteries quite perfectly. So I recreated it in OpenSCAD, making the battery size easily changeable.
I've included two STLs, one matches the Turnigy nano-tech 2S 460mAh batteries, the other matches two Turnigy nano-tech 1S 750mAh. I'm using the second one because I'm still waiting for more 2S batteries and want to use the 1S batteries of my smaller quad in the meantime.
I've printed with 100% infill to increase the strength of the parts. If you want to save weight, you probably can use less.