Call a glass company tomorrow. Simple. Done. We have no idea what kind of services are available where you are.

If you want energy efficiency, though, you'll lose the 'no visible means of support' feature. I doubt you'll gain any added comfort, though. Even efficient windows are lousy energy wasters, probably not even twice the efficiency of the single pane (R 1.7 vs R 0.9). You've got a lot of glass in a small area

But first...Fix that horrible trip hazard on the front stoop.

Have you looked into a custom window pane? Possibly curved if not an exact 90 degree angle?

They call that type of window "aquarium windows". You should be able to have a new window unit made to the same dimensions as the old one. You can at least get some better energy efficiency in the casement sections.

You’ll have the contour or corner no matter what. I’d pull this out and frame.... you don’t even need to match the exterior brick . Do something like black contrasting siding in this small accent area . Place a double or triple casement on left side ( from inside) and up from counter. On right side pretty much fill it in and maybe a hopper or awning or fixed window across ...higher up ....or single casement similar to the other side. I regard something like that as having served its time and you do really want efficiency and can take the opportunity for an interesting detail , esp from the exterior . It will be an upgrade.

These types of corner windows are done often where I live in very contemporary homes and pretty sure where I am they are double paned. You will need to contact a window company in your area.

If you are doing this as a single unit...be sure to sit down when you get the pricing on it.