Palm sugar can be found in Asian stores, in different forms. The Thai brand I used clearly says “palm sugar” on the container. It is also known as coconut sugar, Java sugar or jaggery (at Indian stores). You can also look for Mexican piloncillo/panela/panocha (comes in little cones). Or, if you really can’t find any of those use 1 cup dark brown sugar mixed with 2 teaspoons molasses. Last resort: brown sugar, maple sugar, or date sugar (the latter 2 choices at natural foods stores).