HAG has the Capisco, which I've eyed. There are also kneeling chairs, they tilt the pelvis forward, they can be had cheaply, but I'd hate to buy one just to throw it out. Of course there are the ball based chairs and such.

I sit seiza-style on my chair currently to enforce good posture by tilting the pelvis, but it's taxing after a while, and it took me a long time to adjust to seiza, I use a standing desk in complement.

https://store.flokk.com/us/en-gb/products/hag-capisco?model=...