Oddly enough, Frozen diced onions.
Yea they're very hard to find here too
Back a few months ago, I was given a HUGE amount of fresh yellow onions. It about killed my poor eyes, but I used my food processor to chop them all up, then I divided them up and put them in the freezer. I have enough to last a looonnnggg time.
I'm so happy about that. One less thing to worry about.