This is a Drew Struzan painting, he used to paint all the movie posters but I don't think he did a lot of work for TV.
I'm sure there's some folks out there who might be able to replicate his style but it's highly detailed and likely to cost you a bundle to commission.
Not that this means anything, but I've never seen a poster like that for the shows, not an official one anyhow. Kinda wanna make some now tho
I found this user on deviantart created a ton of Stargate posters similar to this one.
that's really cool. the one with inara in the center I think might be my favorite
You could probably make your own with the assistance of some image LLMs. I got this from a few basic prompts, but with a few hours of masks and in-painting it wouldn't be crazy hard to get the faces right. 
I don't think I'm interested in that, thank you though
There are a lot of photoshopped posters with a similar style, but they are mostly photographic. Maybe run one of those through a painting filter?
Oh hell fucking yeah I just scrolled across this on my front page while watching SG1
Something like this?
something like that, yeah
