You can purchase PROTON 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 Bithumb
Bithumb is one of the largest exchanges in South Korea, allowing users to buy/sell/store Bitcoin and Ethereum.
Go to HitBTC
The most advanced cryptocurrency exchange to buy and sell Bitcoin, Ethereum, Litecoin, Monero, ZCash, DigitalNote, Ardor.
Go to OkEx