You can purchase TERRAUSD from these places
Go to Kucoin.com
The People's Exchange
Go to Uniswap
Uniswap is a secure platform that makes it easy to buy, sell, and store cryptocurrency like Bitcoin, Ethereum, Stellar Lumens and more.
Go to Bittrex
Bittrex is one of the larger crypto to crypto exchanges offering a large number of trading pairs into bitcoin - including all the major cryptos such as darkcoin, nextcoin and litecoin