Just regular super markets, perhaps I've just gotten better at finding the onion free stuff. I've also figured out for some items it says onion powder as an ingredient, but I have zero reaction. It might be just a tiny amount perhaps, not enough to cause a reaction. Or somewhere along the way the recipe changed and a onion substitute is used without them updating the ingredients list. I have also found out the hard way not everything is like that tho and have gotten reactions from stuff with onion powder in them, even in small amounts.

I still remember finding out I was allergic. Apparently my mom knew since I was very small and just made sure I never ate onions. She however never actually told me, or maybe she did and I forgot because I was a kid, who knows. Until I was a teenager and ate dinner regularly at my girlfriend's place. Not before long we ate a delicious rabbit stew, which also contained a lot of onion. I proceeded to be sick for weeks after. My mom laughed at me saying I was allergic to onions and I was dumb for eating something like that. I said she never told me I was allergic, but she was sure she had. I was so sick, I learnt my lesson and have avoided onion ever since.

Yeah it sucks. I can't eat cooked onions as well as raw or powdered. I do a little bit better with green and red onion in small amounts. But it's a risky proposition, so I rather avoid the completely.