I was there a few months ago. For me (without dollars), the best way to get cash was to western union it to myself. They tend to have rates at or around the dollar blue rate. The only painful part of this is that if you send yourself more than around $100 you're going to have to try various western union shops before finding one with enough cash.

The other thing to note is that Mastercard (and Visa I believe) have a newer rate specifically aimed at tourists (the MEP rate), which normally stays closer to the informal rate (blue dollar rate). Annoyingly they tend to charge your account with the official rate, and then refund the difference a few days later.

There's also this website which has a view of all the different rates: https://bluedollar.net/