A number of people have located our handyman site in search of an arched doorway kit (trim kit). I wrote a small tutorial on how to replace an arched doorway and have attraced visitors looking for an arched doorway kit.
The name of the company is Curve Makers. They can be found at Curvemakers.com – Arched Doorway Trim Kit.
Hope this helps. Good luck with your arched doorway project.