Burgher's House: https://amzn.to/2Y9Vx0Q
Town Walls: https://amzn.to/2UF7GsM
Search around a bit and you can discover all kinds of variety.
For Ghosts of Saltmarsh, I also found some excellent naval options to enhance your wharfs and set sail for adventure. Again here, these ships are anywhere from $15 to $20 and would be highly useful for a sea-faring campaign.
It just goes to show you don't have to spend $200 for a sizable ship to add some 😮 to your table. For a little bit more, you can upgrade to a plastic pirate ship model, the Queen Anne's Revenge (requires a repaint).
Queen Anne's Revenge: https://amzn.to/2Crcvyw