You can purchase OST from these places
Go to Binance
To provide users with more secure and convenient block-chain asset exchange services, polymerization of global high-quality block chain assets, is committed to creating a world-class block chain asset trading platform.
Go to Huobi
Huobi (火币网) is a Chinese digital currency trading platform and exchange based in Beijing. Huobi was founded in September 2013.
Go to OkEx