I've started nosing around for maps and so far have found two that are the right size. There is Glory of the Gods (SP edition) and Edi's
Faerun 466, which also has some modded special sites that could be used for fun as well.
That's it that I've found so far that is in the 400-500 province count. If anyone has suggestions, please let me know. I would rather not use a random map.