on good inflatable kayaks?
They’re all over the place. The nicest I’ve come across that don’t interfere with my high back PFD are the Aquaglide Proformance seats:
https://www.aquaglidepaddle.com/collections/accessories/products/proformance-seat
They have a strong supportive back and are height adjustable via inflation. I liked them so much I bought two for my big Neris IK that we use on camping trips.
The raised metal framed seats you often see on fishing kayaks and paddleboards are usually very supportive, and some are height adjustable, but they tend to have higher backs that may interfere with a PFD.