The creator of Secret Agent, Peder Jungck, did license his graphics routines as the
ProGraphx Toolbox to other developers. The toolbox is used in the Apogee games Crystal Caves, Dark Ages and Duke Nukem 1. It's also used in
FBI Fred.
I was looking for other games that might use the ProGraphx Toolbox by searching for games that have data files with a size of 8064 bytes, when I found Little Willy. But alas, the file formats are different.