Your Verbobonc May Vary

 Ran accross a map of Verbobonc on my facebook feed from this guy who is working on this map in world anvil

https://www.worldanvil.com/w/verbobonc-campaign-guide-576cy-stylinlp38/map/93c0c9ec-52f6-4f38-a6b4-2e91836b29db

Reading further he has based his map on this discussion on the dragonfoot forum. Athough the post is from 2003 the links can be revived through the Wayback machine. Here is the map

and here is a link to the gazetteer.

Unfortunately pursual of the Dragonfoot discussion leads to an even older map from the Fate of Itus module. A recreation of the map is shown below:

Although this map may have precedence it's got one big problem. No big river! It's hard to be one of the biggest river ports on the Velverdyva River when all you've got is a dinky creek. This next map tries to rectify this like so:

However I still like the first map better. Jason Zavoda's Hall of the Mountain King blog has a nice series of posts on how to combine Verbobonc with the Night Below Box set and the Temple of Elemental Evil. However, he is using this map:

I understand his choice better when I look at the 3-D model he is using:

This however looks suspiciously like Conwy Castle in Wales. 

Finally, there is this map from the Cannon Fire Atlas:

Which map should you use? Well, that is entirely up to you. I do find it ironic that the one from the most "official" source an actual TSR publication is my least favorite. Greyhawk online has a nice listing of all mentions of Verbobonc in DnD products here in case you wish to attempt preparing your own map.