In OC there is a place in Westminster called JK Electronics, They discount the sealed batteries in half, when they reach the sell by date, and yes there is a "sell by date" on all the batteries.
The batteries work just fine and I have never had one go bad you can pick them up from 10 -15 dollars, depending on what you choose, Supplies are random on the discounted ones and they sell fast.
They have a great stock of new ones, $20 and up,
A great place for your electronic on the water needs if you have the vision and ideas.
