I have a 9.6v 600 mH mini battery from my "late" MP5.  It doesn't want to fit too well in the foregrip on my M4.  I believe I need to have it reconfigured to make it work.  Does anybody know where and how much I could expect to pay to have that done?  Or even if that's the way to go?  I like the punch it has, so I don't want to give that up.  Any help would be appreciated.

Hey!  You can't park that animal here!