I'm assuming you'd just replace it with a rectangular shaped window. In which case, you'd either have to make the whole bigger, or make it smaller and patch whatever is on the exterior of your home. Both could work, it just depends on what size of window you want in there and how easy it would be to match the exterior finish. Paint can fade over time, So you may have a hard time getting a match.

Love that window! It adds so much character to the house that if there is anyway to replace it with same shape, even though pricier It would be great.

Marvin will make one to match most likely, will not be inexpensive but weight it again reframing and the corresponding new stucco and paint for the most likely the entire wall.

The window shape is perfect for the house. Don't remuddle please.

I have to agree please get this custom made I often do not like this type of style for windows but it is perfect for your house.

As millworkman mentioned, Marvin could match this. It is called a "Gothic" top. You could take some of the cost from it and change the Gothic shape to a Trapezoid. It looks like a stationary window; if desired, you could vary the bottom to an awning (s), depending on the width, and get some ventilation.