Stir together the Simple Syrup, lime juice and 4 ounces water in a large measuring cup. Add a couple of mint leaves to each of 4 frozen pop mold cavities. Divide the mixture evenly among each frozen pop cavity, then add the sticks and freeze until solid, about 5 hours.
Unmold the pops and place each in a glass. Top with the seltzer and serve immediately.
Mint Simple Syrup:
Add the sugar, mint leaves and 1 cup water to a small saucepot. Bring to a boil, then turn off the heat. Cover and let cool to room temperature. Strain the mint leaves from the syrup and refrigerate until ready to use.