I want to find the source for this gif i.imgur.com/UMIHUsR.gif but I'm not sure how I would go about that. Reverse image search only gets me don't tread on me memes.

danbooru.donmai.us/posts/1848980

This is the closest I can find. I can't locate the artist's Tumblr.

Refer to this thread instead to look for specific image sources and such:
hypnohub.net/forum/show/10859