Here is the score for the 2nd movement (Larghetto) of JS Bach's Concerto for solo keyboard No. 1 in D major, BWV 972 (after Antonio Vivaldi's Violin Concerto in D major, Op. 3/9, RV 230). So in effect, this is a transcription of a transcription.
And here is a video of me playing the piece.
And if you'd like to have a go at transcribing the concerto yourself, check out the International Music Score Library Project where you can find the original sheet music for free!
Let me know if you find any errors.