We bought a turbo premium and were disappointed to not have backup parking sensors since they come standard on most trims of any new vehicle these days. Mazda sells kits for some models for about $500 or so to add the sensors, but there isn't one as of today for the CX-50. I bought one off amazon for $30 or so and installed it myself. There are lots of them available so browse around. This one had audio only (no display unit - we didn't want one).
Amazon Parking Sensors
It was a little work especially since the reverse lights on the CX-50 are in the tailgate, so I had to get a temporary subscription to the maintenance manual to figure out where the wires were coming from so I could tap into them (the parking light hot wire is the violet wire in the 0940-104E harness behind the left trunk side trim). A manual I found online for the CX-5 kit has you remove the bumper to install the sensors, but that's not necessary. You have to get dirty to climb underneath to work the wires through. Got the job done and it works great. Here's some info in case anyone wants to do the same thing: