Patio door lock

I'm not sure exactly what you're describing, but looking at your photo this appears to be the same kind of hole that matches our 82-218 mortise. I think this might be what you need but look it over and let me know if you had any questions.

I'm still not sure I understand. The 82-218 has a round shaped face and is meant to snap into a round hole exactly like your original. Looking at the information you've supplied so far, I cannot see any reason why our 82-218 would have failed to install. Can you tell me precisely during which step the installation process failed?