The problem with buying batteries for mobile devices, whether they be phone, tablets or laptops, is that most people only ever make one or two purchases from a particular supplier. So someone might be very unlucky and get duff products from a normally excellent source, resulting in a poor review. Conversely, someone who 'hits lucky' with a generally appalling vendor might give a glowing review.
If I was in your position though, I'd consider buying from this eBay seller:
https://www.ebay.co.uk/itm/284373546908
NB: IGNORE the star ratings and product reviews on that page, as they're actually for what is meant to be the same product from
other vendors but which might actually be for inferior stock.
Instead, look at the reviews for the vendor himself (rather than for the actual product) near to the top of the page. He's got 99.5% positive feedback from 2822 reviews. That would seem to me to suggest that he's 'legit' and doesn't knowingly sell rubbish products.