Easiest way to replace this is with a cordless phone battery. I did this to my A2000. They can be purchase for about $10 and are everywhere. There is a particular rating you will need (sorry I cannot remember, but I found the documentation online easily for this), and you have to make sure you solder the correct coloured wires to the proper place on the motherboard for positive and negative. But it has worked well for me (I could not find any place that sold those coin battery holders in my small town). Also the coin batteries do not recharge, while the phone batteries do.
As for why your replacement battery failed so soon: some of these are old-stock. They may have sat on the shelf for years before being sold to you.
