any *good* sources for old model batteries?

[meeotch]

I've read through many, many threads here and on reddit, but overwhelmingly only dug up complaints about fake or under-performing battery replacements for older models, for which Lenovo/Encompass are no longer selling parts. (In my case, X1 Carbon 5th Gen.)

Does anyone have any good sources? There must be at least one known reliable source out there, no? Machine is only 6 years old - there must be plenty of owners that want to keep theirs running.

I've done the "responsible" things:

• Searched "genuine lenovo" on eBay - most of the sellers are either very new, or the photos in their listings have suspicious issues - e.g. the UPC codes not matching the associated FRU, misplaced Recycle icons, etc... And even if I managed to score a for-real lenovo battery, it's likely been sitting on a shelf forever. So I'm not convinced that OEM necessarily beats aftermarket here.
• Searched Amazon - all appear to be aftermarket, and most sellers are new or the items have few/poor reviews.
• Bought one from iFixit, thinking it's a big seller and seems to have good warranty / return policies. The battery they sent had misaligned screw-holes, and a big bulge in the middle. (They refunded me, though.)

I cross-posted this to reddit, but didn't get much response: one person suggested Kingsever (Chinese brand), and another said "Kingsever is garbage". I guess for $35, I can afford to try a couple and toss them out if they're lousy (unless they explode or something). But I was really hoping to avoid playing battery roulette.