I actually get that question a lot - "how can I quickly trade between cryptos, dollars/fiat, etc. if I need to?" I use Coinbase, but been exploring different wallets. Most recently, I signed up for Uphold. Not sure if you've heard of that. Blocktrades is another one I came across just using HIVE.
Best,
Adam
Yeah there are many exchanges that can do that. The ones listed in this post are the major ones I know of.
I use uphold for my basic attention token rewards. Works well but had to get verified.
Yup blocktrades and hive-engine are great ways to buy Hive. I've used all the ones you mentioned.