The piece is in the well-known series Hortus Musicus, along with other
sonatas by Abel. It should be available in any good library. The
listing in the University of Toronto Librrary catalogue reads as
follows:
Author Abel, Karl Friedrich, 1723-1787.
Added author Bacher, Joseph.
Added author Woehl, Waldemar, 1902-
TitleSechs Sonaten für Viola da gamba oder Geige (Querflöte) und Basso
continuo / Karl Friedrich Abel ; herausgegeben von Joseph Bacher ;
Generalbass-Aussetzung von W. Woehl.
Uniform titleSonatas, viola da gamba, continuo
Series titleHortus musicus ; 39-40
ImprintKassel : Bärenreiter-Verlag, c1949.
Publisher #Bärenreiter-Ausgabe 1085
Publisher #Bärenreiter-Ausgabe 1745
Contents notev. 1. E-moll (Nr. 3) ; D-dur (Nr. 4) ; G-dur (Nr. 6) -- v.
2. C-dur (Nr. 1) ; A-dur (Nr. 2) ; A-dur (Nr. 5).
General note Includes alternative part for violin or flute.
General note Pub. no.: 1085, 1745.
General note The figured bass is realized for harpsichord.
It is definitely the piece you are seeking since the MIDI file you
provide a link to matches. If you don't have access to such a library
let me know and perhaps I can scan it for you.
Peter Newton