It is hard to find an operating sidelight. I have had success in using a 17 casement by 71 inches and keeping it up off the floor a little bit matching the height of the door.

Check with a clad wood window and door manufacturer named Eagle. We've used their ventilating French door sidelites and they're very well-built. If I remember correctly, Marvin had also submitted a proposal for the specified venting sidelight product. However, I'll bet you'll find a standard color match with Eagle due to their close relationship with Andersen.

The idea posted above was a common approach to achieving ventilation at a main entry before operable French door sidelights became popular. It looks a lot nicer with the venting French door sidelight, as the door stiles and rails align nicely. This is not possible with a standard casement, as the sash profiles are much narrower than a typical French door. However, you might verify that the stiles and rails align correctly between the Andersen and Eagle products, as it is unlikely that they will identically match.

Thanks so much!

I recently saw in the paper sidelights that are screened and hinged to open into the foyer. The reason for this is to avoid a storm door which covers that beauty of the center door.

I looked at my 2008 Andersen catalog and they have casement windows (CR16) that have glass openings of about 67x12 inches. Seems like that would be tall enough to roughly match the glass in a french door. You'd have to trim out the top and bottom to match the door. Just a thought.