According to a 1907 reproduction, the 1842 article was published in: Abhandlungen der Koniglichen Bohmischen Gesellschaft der Wissenschaften.
The 1907 reproduction, apparently under the auspices of H. A. Lorentz, can be found at: https://www.deutsche-digitale-bibliothek.de/item/PX6IXQLYSSVGGDQSZHMHONP5KWBS4FWL
An English translation of Doppler's 1842 monograph can be found in the book by Alec Eden, "The search for Christian Doppler"
Is such an important article only available as a reproduction?