Where do I get a new car battery for my Mercedes E350?

I can see how this question is necessary! 

My first (and most obvious suggestion) would be to get it from a dealership, or at the very least get their suggestion about places to purchase one.  The next step would be to check out auto part chains (National Tire and Battery, Autozone etc..).  Lastly, (as a last source) I would check online autopart stores.  Here is a list for you:

• Interstate Batteries
• Batteries Plus
• Pep Boys
• AC Delco