Try mexsican shops. Being on the edge of farm country, I 've been able to find Mexican Pepsi in the mexican party stores.
I have tried looking at those places. All I have found is coke, sprite, fanta, and squirt plus some others that I don't know what they are. There used to be a pop store that sold it but I talked to the owner and asked him when they were going to get more and he said he had not been abel to get any for a while now.