Add door lock beep to 2014 Prius C 2?

Girlfriend just bought a 2014 Prius C 2 that has all the features she needs except one that's really annoying, a lack of any audio feedback on locking the doors w/ the remote. I thought it would be an option that could switched on via Carista (OBDII phone app), as it can w/ my 2012 Prius V (I think trim level 4), but apparently according to other threads here that's a feature reserved for the Prius C 3 and up.

Any way to buy an OEM part and plug it into whatever wire harness is probably sitting empty somewhere in the dash? Or an aftermarket solution of any kind?