While it's not something that's been on my shopping list, I decided to look around at our local stores. It looks like H-E-B offers fully cooked hamburger patties. $10.39 for six 3oz patties. I don't think they ship, but it could be worth a look.
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If you have a membership, Sam's could be an option. 12 4oz patties for around $18.98.
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Now, I'm guessing this is what you normally bought...
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I found them at several stores online, but I don't think any of the chains are in CA...with the possible exception of Dollar General. They supposedly offer delivery, but I'm not sure how far nor do I full trust buying food items like this from them. I'm sure it's fine, but I get a little spooked buying regular food at dollar stores.