It’s a little late now but supermarkets special order kosher foods all the time.
I used to live in a very rural area with few Jews (never mind observant Jews) and special ordering kosher meat and other products was the norm.
If you hurry and get to your local market they may be able to get it in before Passover is over. This should have been done two weeks ago to ensure you have your product by Passover.
The supermarket and Coke will be happy to accommodate you. They do not want to be accused of being anti-Semitic.

The supermarkets in my area have no shortage of KP Coke. It would seem that of the 4 markets I patronize their entire stock of 2 liter Coke is KP. The Pepsi on the other hand seems a little harder to find.