I've read on the /r/gamedev subreddit of people succeeding with even just doing cold-call emails to popular twitch streamers. Someone recently posted a breakdown of how many streamers played their game after he sent out emails, and he seemed to get around 5% turnaround.
There's a guide that was posted to this subreddit a while ago too, that gives what you are looking for I think. https://www.reddit.com/r/gamedev/comments/m74fcj/guide_to_ma...