You can purchase GEMINI-DOLLAR from these places
Go to Bitfinex
The largest and most advanced cryptocurrencies exchange
Go to HitBTC
The most advanced cryptocurrency exchange to buy and sell Bitcoin, Ethereum, Litecoin, Monero, ZCash, DigitalNote, Ardor.
Go to YoBit
Buy and sell Bitcoin (BTC) on YoBit Exchange!
Go to OkEx