How we get through a grocery trip in one piece

The grocery store has always been incredibly hard for Seth. He has gotten better, but for a while he would clench onto my shirt for dear life the whole time we would be in the store. He would cover his eyes, his ears, anything he could do to get away from the situation. He would either scream because he wanted to leave or because he wanted to get down and obsess over the wheels on the cart. Our trips usually ended with him screaming and me frustrated because I'd only gotten half the things on my list. Not a pretty sight. Anyways, ever since he had that "awakening" in July he's been doing a lot better at the store. I've been trying to get him involved with the whole process. My grandma made Seth a little library bag last Christmas and I bring it with me. I give it to him as his grocery bag and we fill it up with his special foods. I don't know why I didn't think to do it before. He loves having his own bag. It keeps him engaged during the entire trip. Thanks grandma!