Does anyone know how to not receive the Riolu egg from Riley in BDSP? In Brilliant Diamond, I managed to get him to not give me the egg by catching a couple Pokemon on Iron Island to make my party full and having 4 full PC boxes, and I'm trying to do the same thing in my Shining Pearl save, but not having the same luck. Even with a full party and 4 full PC boxes like in my BD save, Riley is still giving me the egg on my SP save.

I don't want the Riolu egg. How can I make him keep it?