Who said buy a frame only? Not me. Your parts might not be compatible.
If you like the Jamis, fix it. Take it to a frame builder and have them weld a new hanger on it. Do nothing and make it a SS. Problem solvers makes a replacement hanger, but it's probably not a great long term solution.
Their are so many options for a steel frame bike that is comfortable and upright. And like @ChrisLsaid, any shop should be able to modify a fit for you. I've done it myself. It's not expensive or difficult.
Weld a hanger on the Jamis and replace the stem. Problem solved for under $200. Shops have software to plug in your bike's geometry and show you what a new stem would look like.