Battery for IBM Thinkpad T43

I need to buy a new battery for my Thinkpad T43. Problem is that I know nothing about batteries. How do I select a high-quality battery that will last for a while? A good manufacturer and retailer?

Buy one from Lenovo .

I don't trust e-bay batteries for ANYTHING

What about non-ebay 3rd party stores?
laptopbattery.net
atbatt.com

etc...