CLARK(E), The Chequers, Hatfield, 1792-1832
HALS has a large collection of old photographs, and if they have anything suitable you may be able to pay them to make you a copy. The Hatfield Public Library may also be able to help (address via the Herts County Council site) and may have more local knowledge. There are also a number of books of old pictures - but in all cases there may be a problem identifying the building of interest. (See Looking for Books)
As an example the following reconstruction, from Hatfield: A Pictorial History, shows the location of the Chequers.
Part of 1790s reconstructed map of Hatfield
The books also includes the following picture:
The Eight Bells, Hatfield
If you compare the picture with the map you can deduce that the photographer was outside the King's Head (corner just visible on the right), and the Chequers is, unfortunately, just out of picture on the left - but that adjacent buildings in Duck Street are identifiable.
The map does not show the Sun. Information on Hatfield pubs is published in Hatfield and Its People and while this is very difficult to find (I don't have easy access to a copy) you could enquire to see if the Hatfield library may be prepared to photocopy relevant pages.