Welcome to the Forum!

If you're looking for a name brand, the only one I know is Cardinal. If you can get them fabricated locally, that is certainly worth looking into. These are steel steps and benches. I've retro installed a number of their steps into steel walled liner pools and they work out very well (* as long as the installer pays attention to detail!)

I've also, many years ago, retro'd in 'crete steps for use in plastered pools.

Whichever way you go, you WILL need to have a custom liner made to properly fit the pool (guess what... I've also had to do the measurements to send to the liner manufacturer )

I can help you with this project, but need to know exactly what you need to know and which way you'll be doing the stairs and bench.