Alright, I figured it out. That piece is called the '''saddle''', and it's connected to the arm.
I can't find anywhere to buy just the saddle, but by searching "dji mavic pro left rear arm" on ebay I found an entire arm with an intact saddle for $30 with shipping.
It looks like you can also buy them from [https://store.cloudcitydrones.com/dji-mavic-pro-back-left-motor-arm.html|Cloud City Drones], but they're out of stock at the time of writing.
Will update when it comes in!
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'''2017-07-18 edit''': it came in! Confirmed that that piece is part of the arm. Replacement was pretty straightforward - just a bunch of screws and minimal soldering. Some parts of prying the case apart were tricky, but nothing harder than an iPhone screen repair.
Alright, I figured it out. That piece is called the '''saddle''', and it's connected to the arm.
I can't find anywhere to buy just the saddle, but by searching "dji mavic pro left rear arm" on ebay I found an entire arm with an intact saddle for $30 with shipping.
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It looks like you can also buy them from [https://store.cloudcitydrones.com/dji-mavic-pro-back-left-motor-arm.html|Cloud City Drones], but they're out of stock at the time of writing.
Alright, I figured it out. That piece is called the '''saddle''', and it's connected to the arm.
I can't find anywhere to buy just the saddle, but by searching "dji mavic pro left rear arm" on ebay I found an entire arm with an intact saddle for $30 with shipping.
Will update when it comes in!