Flat-arch doors are more widely available on the retail market than true and elliptical arch doors. Check out options from Marvin, Jeld-Wen and Pella. Tip: If you are interested in replacing an existing rectangular door with a radius-top, I recommend consulting with an architect and/or engineer to ensure that all structural implications are considered. In many homes, such a swap might require a little cutting and patching, while in others (particularly with stone structures), the job might require professional opinions and oversight.More: 10 Extraordinary DoorsGreat Ideas for Pocket DoorsBarn Doors for the Home