Bittrex has opened up new registrations. Get an account and verify. Meanwhile you can use binance to sell Steem. You can use the internal market for a SBD->Steem quick conversion. Send Steem to Binance and sell it for btc. You will probably pay less this way compared to blocktrades.

Getting a working bittrex account is important. I've recommended it to a few people who were unable to get accounts before. But there's a small issue. Even though the verification happens quickly, they take a while to enable the account which in some cases remains disabled for some people for many days.