You are in the right place. Most all of the Mustang supply places carry convertible tops for the classics. For instance, on page 237 of the Mustangs Unlimited Catalog, you can buy a vert top. Give them a call at 1-888-398-9898
If the metal is still good, just refurbish it by painting it, then add the new cloth top and back window that comes with it. Here are just a few other sources for buying a new top. You can also buy frames and wells from these places.
Texas Mustang- 1-800-527-1588
NPD (National Parts Depot) 1-800-368-6451
Give us a holler if you still can't find what you are looking for.