I have a airsoft battle tonight with some young men from my church and found out one of my battery packs has died and I need to get a new one today since either a young man will be without a gun or I will be relegated to the role of suicide bomber or collateral damage
Is there a store in the area that anyone would recommend?
Look for hobby stores, anywhere that might sell R/C cars and planes should sell NiMH or Lipo batteries to power them. You may have to tape the battery to the outside of your gun if they don't sell a pack the size you need, but that's better than nothing. You'll also have to make sure you get a back with the correct connector and the correct polarity. In Airsoft, small tamiya connectors are attached with reverse polarity relative to R/C packs.
If you want a drive, Google turns up Harland R/C hobby shop near Howell:
1732 N. Old US23 Howell, MI 48843 (810) 632-0106
I'd call first to make sure they have what you need.
Google also gives a description of "Just 4 Fun Hobbies and Comics" has having R/C cars and planes, so they might be a closer option. They're located at the Frandor mall.
300 North Clippert Street Lansing Charter Township, MI
 Last one.
Radio Shack's website lists a 9.6v R/C pack that would work. I don't know if you'll be able to find it at the store, but it's worth a shot:
From what I hear Hartland R/C hobby shop should be able to help you. It's right near my house, but I've never been in there. I have heard of people getting batteries for airsoft there, it is quite a drive from Lansing though, you'd be looking at about 45 minutes or so.