trailer/MH type not mentioned so I provide info from 5th wheel experience.
Fixed a damaged baggage door and had new one in hand to replace. old one came out real easy and then found out how easy to change parts/cover, adjust frame....repair of the damaged one was very easy..
Go buy door the size or close to the size you want and cut down to size.
Cut the door opening to your new dimensions and install.
Gary & Cynthia