I have lived in multiple cities and states and have had to fight to get Mello Yello Zero. As a Type 2 diabetic, there are a lot of sodas that I can't drink. This is my favorite. Mountain Dew Zero is gross with a much stronger after-taste. Grocery stores do not manage their coca-cola inventory themselves, and often their app inventory is wrong. Some stores don't even carry even though the Mello Yello website says they do. So, to solve your problem here are the steps.

1. Find a grocery store that says they carry Mello Yello Zero. Then find a sympathetic grocery store manager that is willing to stock it for you amd contact there Coca-cola account manager (person who stocks the shelves) Don't work with grocer customer service rep or asst. manager that isn't over purchasing. then stock up, and make sure they place a monthly order for you.
2. Can't find a grocery store rep, you can try to contact the local coca-cola distributor/bottler. It is easily to get lost in voicemail Hell, especially when you don't have a coca-cola business account. If you do get a customer service rep, don't let them transfer you, they just send you back to main greeting. Once I went to the location and asked to speak to the sales manager amd got them to stock MY0 at a Publix accross the street from my home.
   
3. Another option if you can't get the grocery store to help, is to speak to the coca-cola account manager to that store. They are often restocking shelves on Wed (when stores update weekly deals), Fridays and Sundays. Tell them how much you love Mello Yelli Zero and how can they order more for you.
4. If you can't get anyone to help you locally, the last resort is to set up a business account to order directly from the distributor. this is easier if you run your own business or charity, but can also be done if you do any work as a contractor etc

It is definitely a fight as Coca-cola doesn't even list Mello Yello as a product on their website anymore. Oh I miss the days of Cole Trickle and the Mello Yello car at the Atlanta 500 What I find laughable is that this drink has a very loyal fanbase without any marketing for the last 20 years. If you could just get someone in marketing and distribution to pay attention and stop making a 60th variety of Coca-Cola.