I have gone through the same thing.
What I have found as the best way is to look at the MODEL NUMBER of the battery (printed on the battery itself or on a sticker on the battery) and enter ONLY that into the search bar of your browser.
Skip over e-bay, or used batteries- look for Amazon.
Disregard any and all information about what devices the battery fits (or won't fit) and any other thing like that.
If the model number matches exactly, then it is the same battery.
Some differences may occur in the rated amperage, don't worry about this because different manufacturers can rate batteries differently- or the specs may have even changed over time.
The main issue you will have is the date of battery manufacture.
Most batteries are produced only a short while after the device they go in is discontinued.
So your new battery may actually be about as old as your device.
These batteries degenerate from time as well as use, so you may not expect to get the same performance as you did with the original.
That being said, I have had very good luck with three battery replacements on three different devices.