You can purchase TETHER-EURT from these places
Go to Bitfinex
The largest and most advanced cryptocurrencies exchange
Go to Bitstamp
Bitstamp is run from the United Kingdom and is one of the most popular fiat to Bitcoin exchanges.
Go to Kraken
Buy, sell and margin trade Bitcoin (BTC) and Etherum (ETH) in exchange with EUR, USD, CAD, GBP, and JPY.