I hate to tell you this, but the best thing to do is avoid the processed foods aisles. Those foods generally have high carbs (and really junky ones, at that). Your best bet is to stick with the fruit and veggie aisles, maybe dairy.
If you're really desperate for breakfast cereal with high carbs, you can try cutting the serving size in half and then replacing the food with something that has very few carbs (like eggs). I'd recommend something that doesn't have a ridiculous amount of sugar (like Multigrain Cheerios) if you want to try that.
I make almost all of my own food with nothing processed (except for oatmeal and dairy and other things I can't possibly make at home) because I'm banned from practically all carbs. It's NOT easy and I don't think it will ever be, but it does get easier.
One more thing--I was diagnosed with a food allergy more than 6 years ago, and I still check my favorite "old" foods that I haven't been able to eat in years to see if they've magically taken the peanuts out of peanut butter. Give it some time, you'll get bored of checking, but if you're anything like me, you'll still go down those aisles occasionally just to check.
I wish you lots of luck!