I was happy to find a piano accompaniment for the Dittersdorf Concerto for Bass #2 on Musescore.com today. I have a student wanting to play it for an audition. It is generally played in D Major on the modern double bass with solo strings tuned up a step so the piano accompaniment and orchestra parts would be in E Major. But he doesn’t have solo strings and wants to do the audition in D Major so I was able to download the piano part in Musescore format and instantly transpose it to D Major and also export an MP3 file for him to practice with. Life is so much easier (in some ways) for young musicians than it was when I was starting out. I had to make the trip to Patelson’s to buy my parts.
Anyway – some good soul has put a very nice version of the concerto here: https://musescore.com/user/30719460/scores/6816745
And I can’t recommend Musescore enough. Free for all platforms.