Do you think we haven't found that already? We have been in the same position as you are when we tried to buy for first time. Everyone first goes to Coinbase. It is the biggest exchange, having volumes and a good trading user interface. But, it has the worse customer support out of any cryptocurrency exchange. I think that possibly this is an issue of Coinbase having to trust employees and even limited access may provide vulnerabilities that can be exploited. Since it holds and manages such a huge number of volumes it needs to be very strict, even if this means less customer satisfaction.