I only know of Canadianbitcoins.com, name some that you've tried previously?
Where do you get bitcoin?
if you buy bitcoin in one place and then you should be able to sell as well in that place.
There is a lot of bitcoin or crypto currency exchange currently, but I only use binance and my local exchange.
You can see in this site to know how much crypto currency exchange in this world
https://coinmarketcap.com/rankings/exchanges/