If it's a computer I care about using, the only options I will consider are new old stock Apple batteries or NewerTech Nupower batteries.
I have bought quite a few new in box Apple batteries that have worked perfectly. I've bought 6 new old stock Powerbook G3(Lombard/Pismo) in the last couple of months and all have been perfect-they charge and work for their originally rated time. Several months back, I bought an unused Powerbook battery for the 3400c/Kanga G3 and it was also perfect. For some perspective, 3400c battery was probably about 18 years old and the G3 batteries about 14 years old.
You are at an advantage with the 5,5 since Apple was still making them up to a year or year and a half ago. You can probably find a relatively recent production one if you look enough.
I've had several NewerTech batteries and all have been at least as good as an Apple battery if not better. They are pricey, but not too long ago I splurged and bought them for both my 5,5 and my MBP 4,1. I've had several of their PPC laptop batteries also. The fit isn't quite as good as an Apple battery, but it's close and functionally they are perfect. Plus, if you have an issue, you can actually track them down to get service
I've bought a bunch of cheap eBay batteries-some directly from China and some of similar branding from US sellers. Most of these have been Powerbook and iBook batteries. I've sometimes been through two or three batteries from one seller to get one that would actually charge, charge all the way up, or last any decent amount of time. I had one in my 5,5 that would cause the computer to randomly turn off, and a few months later quit charging. I've had cheap batteries start to bulge in less than a year.
Just this past week, I bought a Macbook Air 1,1 from a friend. He'd removed the battery before selling it to me because it was bulging. This is a computer for my collection, although also one I'd like to be able to use. The missing battery causes throttling(the 1.6ghz C2D can't exactly spare a lot of CPU power for that) and also makes the computer feel flimsy. To add to that, the charging port has to be the most awkwardly placed of any laptop in history(it's on the bottom) and it's really easy to knock loose when you're using the computer. I'm still trying to figure out how Apple had the audacity to charge $1800 for this computer