Where can I buy the keyboard ZIF connector?

Didn't replace the upper case. Popped the old keyboard out fairly easily. I did that by disassembling everything to get the chassis on its own, grabbing the edge of the chassis with both hands, and forcefully shoving the corner of the keyboard toward the inside with my thumbs until the first few rivets popped. After the corner was pulled up enough, it was as simple as holding the chassis down and yanking the keyboard out the backside. Sitting the new keyboard in place, you can then reapply the backlight and the screws in the center of the keyboard, and reassemble the system. Most of the keys are rock solid, with only the slightest extra deck flex on the bottom corners if you're actively looking for it. This saved me a TON of buying a replacement chassis, as the laptop was sold to me in MINT condition externally. If the slight extra flex on the corners is undesirable, you could carefully remove the old rivets with something like a PCB drill bit the size of whatever screw you're using and only plunge like 1mm (just make sure you don't drill THROUGH) and you'll be able to make the screw self-thread. Amazon has MacBook keyboard screws meant for replacing these rivets. The ones on this MacBook unfortunately don't pull out of the chassis as easily as they do on some other systems, like the older MacBooks or the Surface Book, hence the possible need to drill them out. You should only need to do a few near the bottom corners to get OEM-like keyboard feel.