I think you may find it easier to find double doors at that width. You could use glazed French doors that you can paint to look like crittal if that fits with your style. This would all maximum light, would be in line with the glass panels at the top and you could pick up these kind of doors quite cheaply. You would need a decent carpenter or someone with good diy skills to fit.

Hmm, I wonder if there were sidelights that got filled at some point?

You could try Green Doors. They have a plethora of reclaimed doors (from antique to brand new) and a lot of the doors will even come with the original door frame. I purchased my front door from them a couple of years back.