I"m not sure if this will help you or not, but you might want to google these places and see if they can help you in any way. I know a supermarket sounds crazy but from what I hear Mexico's idea of a supermarket is different from ours, you never know they could have exactly what your looking for.
Chedraui Supermarket - Grocery Store in Playa del Carmen
This is biggest and best supermarket south of Cancun. They have a large selection of import and national food items, fresh veggies, a bakery, household items, clothing, etc. Essentially US style shopping. ------ When coming south from the airport, as you approach Playa del Carmen you will go through two sets of traffic lights. As you go through the second set, you will see a big shopping plaza on your left, it is orange. Keep going south and you will come to a "Returno" which will allow you to U turn and go north. Take the U Turn and stay in the far right lane, and you can enter the plaza from there.
Location: on the main coastal highway from Cancun, just south of Av. Juárez, the main entrance to PDC
Panaderia del Carmen - Grocery Store in Playa del Carmen
Baked goods and bread.
Location: On 30th Avenida, between 6th and 8th street
El Molino (excellent cakes, esp. pastel con tres leches) on 30th a bit south of Juarez