I was looking through the clearance racks at Target and Walmart.

I notcied they had these air hog Lipo battery pack upgrade on sale for $7.50. I wasn't sure how big the cells were so I only bought one. It is really easy to break the plastic cover off of the cells. I used a small knive on the top of the battery to cut into the bumped out sections and pry the plastic off. This assured I had some room from the lipo packaging.

The batteries are probably the same length as a AAA battery and holder. I think they would work fine mounted on the side of gen1 xmods. I'm not sure if the bottom of an evo could house two of the cells. They would definitely need a little modification.

All-in-all though, finding two cells with a charger and not having any shipping cost, 7.50 is a really good deal. I'm also assuming the charger will be easily modified to charge other packs. I don't know this for sure as all my tools and everything is packed for my move. I definitely think I will be buying at least another two sets of these though.