How to Practice Openings When Opponents Rarely Play Them?

One way to practice openings is to find a partner who also wants to practice their own openings. Then you alternate games... with your partner playing into your chosen line in one game, while you then play into their chosen line in the next game.

That's exactly what I am looking for, but I don't have any friends so I was hoping there might be an engine that was designed to help with this.

You could start a thread in the Openings Forum : "Does anyone want to practice openings?". You could even specify a rating range, and announce that the thread can be used by other players to find opponents once you've got yours. 

you can preset positions in daily chess challenges if they are not rated, try that

Side note, If you want to practice the pirc I would be down to play daily games with you, challenge me if you want to.