Recently, a friend of mine got a 12 Volt dry cell (PB) from Oddyssey, a company that makes a wide range of batteries that are used for heavy duty applications. These cells can be run completely dead up to four-hundred times without failing. During a comparative duty test, the single Oddyssey cell lasted just as long as a pair of equally sized flooded cells, that were wired in paralell, did.
Here is the company URL http://www.odysseyfactory.com/
I'm totally impressed with their products. They make chargers too. Plus, the batteries are packaged very nicely. The model I saw had a well-designed carrying handle. If you need some batteries, it might be worth checking what they offer.