You can purchase AVENTUS 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 Gatecoin
Gatecoin is a bitcoin and ethereum token exchange based in Hong Kong. Trade BTC and ETH worldwide with USD, EUR and HKD.
Go to Mercatox
Go to EtherDelta