Need to change typing sound (need real clicks, not pockety-pockety)

My wife's iPhone SE is driving me nuts, with its multi-toned "pockety-pockety" typing sound.

Turning typing sound off is not an option --- how can we change the sound to a real "click"?

I really hope Apple hasn't dodged this important customization. I can't find anything about how to do it on the Internet.