I used iFixit batteries in both my iPhone 5 and 5s. They are pricier than Amazon & eBay fare, but I was swayed by the positive reviews.
If you're looking for a good toolkit for electronic repair, I also recommend the Pro Tech Toolkit. The magnetic project mat is super handy, too!
If there's no hurry, iFixit will email a notification when stock is back in. I had to wait about two weeks for my 5s battery.Their webpage is pretty full of "SOLD OUT" labels.
If using amazon, check the listed capacity is at least equal to or above the original and also the seller's reputation.
I've had good luck from an amazon seller in Quebec for Mac portable batteries.