For sunscreen, I think Disney usually has a contract in place with a company, and you will only find products made by that company in any store on Disney property.
As PP mentioned, you can have it delivered - Instacart,
www.TurnerDrug.com, possibly even Doordash (in my home town they will do deliveries from Walgreens).
Or you could ship a small box to your hotel.
I used to assume that since it's Florida, all of the stores would carry lots of different types of sunscreen, but I have learned that this is not the case. I've been to Publix and CVS there at various times and discovered that a brand I wanted was something that they did not carry, or they carried it but were sold out.