26R battery for 2.4 Ltd petrol

Hello everyone,
I'm the newbee so please be gentle.
I have a 2007 2.4lt Ltd Cabrio with a knackered original battery. Apparently the original Mopar part number 04671579AB is no longer available and I keep getting quoted a "Fiat" part number of 71771427 by Chrysler people.

I have looked at other makes but every tyre & battery place I have visited all seem to offer different products with varying specs and quote for a Right positive layout instead of the LEFT positive layout it should be?

I would welcome any advice or suggestions anyone can offer (part numbers/suppliers etc). Thanks in advance.

I had the same problem last year when my battery just wouldn't hold a charge, in the end I managed to get an Exide battery that fitted, although it wouldn't fit inside the battery blanket, the Exide part number was EA640