Hi,
I got a new battery 2 months ago brand new from Lexus and cost me £89.
I did some reasearch and in the end went to the dealer as the price was not that different to others, but had the peace of mind that it was the correct one and the terminals the correct way round.
I would agree with Normski, to reaplace with new battery if yours has been in there since new.
Its very heavy to carry thou. My car was dead to I had to carry it on the Tube and back home.