I had zero luck in my online piano bench search a few years ago. I finally found a damaged Jansen Duet at a local dealer/repair shop that they gave me a deal on, which then I fixed up. So, you may have better luck if there's a piano repair shop in your area, also asking a local technician could be good: they and their colleagues often come across used/vintage items like benches (if the piano was thrown away but the bench was fine) that they don't necessarily have a ready means of selling, storing, or repurposing.
What's tricky with online piano bench orders is that anything actually sturdy risks being disproportionately expensive to ship. So most online "deals" will get a bench that comes in a very thin box which then you assemble, and I never trusted that kind of build quality for this purpose. It's also possible that a chain music store that will necessarily have to freight ship products between distributors and store locations will again have a better deal per dollar on quality, as their shipping costs are distributed across a large product line of pianos, organs, etc.
Spotify:
https://open.spotify.com/artist/2xHiPcCsm29R12HX4eXd4JPianoteq Studio & Organteq
Casio GP300 & Custom organ console