Doors from a lumberyard. Also stacking door hardware from Haffele also available from a good lumberyard. You can try Dykes Lumber in Brooklyn as a good starting point.

Fleetwood. Western both mfg awesome aluminum. Just completed our third home with Fleetwood. @rogerc I've done two homes full of Fleetwood in that price range. There could be a significant cost for the beam above with posts and footings to support. At this span we're usually at steel with a moment frame setup depending on how many walls remain for lateral structural values. The imaginary rectangle around this unit needs to be very stiff and inflexible.

I actually don’t know yet. Just getting started. It’s for a beach condo on a salt water bay built in 1970s. Current windows are wood but are rotting. Don’t know pros/cons/costs yet of options to replace. I wasn’t sure if what I was looking for was only available in certain materials so that may be a limiting factor

Thanks @millworkman. I am asking manufacturers and window reps, but figured I'd ask here to see if anyone had done this previously - curious which brands will do it and if anyone had experience with the pricing increase! If I don't hear from anyone, I will try to report back with what I find out.