This is the only place I could find an exact match (https://www.aliexpress.us/item/325680233...). Unfortunately, it won't let me log in, and delivery times appear quite long (to US): about two months.

Yes, but where can I get one? A lot of what’s available on Amazon (for example) has reversed polarity (black/red switched). Be great if someone could post link to specific product. I just replaced batteries in two Lenovo Yogas (4 years old), from IFixIt. And independently sourced battery for my Jabra 75 headset (5 years old). I’m a total convert!

Great instructions, as usual. This was my second battery replacement (two separate computers: 720 and 730). They look similar, but screws are placed differently, and case comes apart in the opposite direction. Battery is the same though. Since they were 3 and 4 years old, the batteries were totally shot, and computers would shut down suddenly, even when apparently at 100% charge. I'm hoping this replacement will keep them going a few more years.

That battery connection is really small, it's hard to get much leverage to reconnect the new battery. Still, as others have said, pay attention to the orientation of the connector, make sure it's aligned, and be patient. If you line it up just right, it'll glide in. Make sure it goes in all the way.

Overall, this was very helpful: pictures were good, it took about the time proposed (I'm a newbie at this kind of thing), and since I had a 720 and a730 that both required new batteries, I bought the toolkit which really helped. I would add that, in the first step, where you're prying away next the hinges, there appear to be a some small 'nubs' between the hinges that hold the case in place. It doesn't mention it, but you have to work your way across between the hinges, to make sure it's loosened, otherwise the case won't come apart. Other than that, I found everything went exactly as described. I Fixed It, so thanks iFixit!