There's a local online store called Vitadeals. They have all the hard-to-find stuff, like ashwagandha extracts, 5 HTP and so on. Prices are pretty reasonable and delivery is fast. You can also buy from their warehouse in Pasir Ris.
How old are you? If you are an adult, it's probably "adult acne", caused by excess estrogen. You can take a supplement called Diindolylmethane, or "DIM". It's very effective for adult acne.