Had an emergency yesterday, 500 miles from home, when my 2011 MacBook Pro booted to a "no operating system found" message. I'm very technically inclined, and was able to trace the problem to either the drive's flexible cable, or the SSD drive itself.
Option A sounded more likely, so I called 25 of the stores in Phoenix & Scottsdale that put themselves out there as a Mac repair experts. Of the three that said they had the cable in stock, Mac I Am was the only one who would actually sell it to me without paying about $100 for installation. At $40, it was cheaper than the Uber ride there and back, and it took me less than $10 to install. Highly recommend!