I've been loving the [relevant (true) complement based on the work in your discipline] coming out of the [Company Name] for the past few months, especially the recent [relevant post, design, rebrand, feature, update and a quick note showing you actually looked at it].
One of my acquaintances, [name of connection] is a contributor to the [Company Name] and she recommended I reach out to you to see if it'd be a good fit for me to contribute as well. Right now, I typically [one liner about the services you offer and niche that it's in, showing your clearly a good potential hire for them].
[If possible, add an extra sentence highlighting relevant past work or offering up more industry credibility boosters.]
Let me know if this sounds interesting and I'd be happy to put together a few ideas on a [deliverable] we can test out!