I have a Dell XPS 17 (L702X). It was near-top of the range when I got it but now its positively ancient (8 years old next month). Despite that, it still seems to do pretty much everything I need, and I don't want to replace it just yet. But about a week ago, I started getting battery error warnings, and the battery now drains much faster than it used to.
The Dell US website offers a replacement (but with a smaller capacity) for $135.99 (the UK website doesn't seem to have any batteries for this model).
I've also found a variety of third-party batteries for sale on Amazon etc, all cheaper and larger capacity than the one from Dell (but still smaller than the original). E.g.
£15.99 ARyee
£24.99 Bay Valley Parts
£49.99 Duracell
Plus some other more expensive ones that I didn't save the links to.
Never having bought a laptop battery before, what should I look out for? Any brands to prefer or avoid? What sort of price is too cheap to be trustworthy or too expensive to be worth it?