Fenimore Fillmore: The Westerner, a remastered version of the 2nd game in the series (Wanted: A Wild Western Adventure) was just released on GOG and is currently 40% off.
Like the previous re-release (Fenimore Fillmore: 3 Skulls of the Toltecs) it comes with GOG achievements.
P.S.: GOG also released some other (non-adventure) series which people with Steam aversion can finally enjoy. Although in the last mentioned series one game is missing which title I cannot remember anyway.