Beeing out in the wild with my flashlight and doing the strobist requires always a spare set of full batteries. To keep them together I made these small cups to be placed over the ends of the batteries to keep them together.
I figures out that the accuracy of my printer ( Leapfrog creatr ) messes a little bit with the perfect fit of the parts. I would recommend to give it a try first and test the fit. If printed correctly the caps should slide over the batteries a little bit tight and should keep on.
I used a small rubber band for the ones that does not fit perfectly.
Available is a size for AA and AAA.
Maybe I will try to make a mould out of these and make some rubber ones.