Do they exist? Short answer is: no.
The reality is that posture does not really matter when is comes to experiencing pain. At least as not as much as we once thought. Given the heterogeneity between body types and abilities, it's impossible to be able to say that any one position is fundamentally 'good' or 'bad.'
There are some specific situations where considering posture and body mechanics comes into play, but for the most part, any posture can be a 'good' posture. And in my opinion, your next posture is the best. Change things up, often. Movement is the great healer and pain preventer.
For more on why posture doesn't matter, check out the video below. Dr. Greg Lehman is both a chiropractor and a physical therapist. He has investigated biomechanics and pain science extensively, and in the video you can get a glimpse into some of his thoughts on the matter.
For any PT's reaching, check out Greg's course on Reconciling Biomechanics with Pain. Full disclosure, I haven't personally taken the course, yet. But a former co-worker did last year and she raved about it. We had a great discussion about the course content so I won't even hesitate in recommending it for others.
That's all I've got for today. Thanks for reading,
Dr. Piotr