I had to do this to mine aswell battery started to die out. So i looked up what i needed to know in this thread
http://www.xoutpost.com/articles/x5/...ernatives.html and than went to sears and got a die hard battery for international branded vehicles. Sales person double checked what kind of battery i needed to make sure it would fit and found the die hard. Battery was just about the same but the OEM one was White and handle was different while the die hard was black. Both had the vent plug and it still works after a year. Hope that helps but in the mean time ill try to find that battery i have from die hard for you so you can get if you like.