There use to be a unit called "Rhythm Bandit" from Lueken Innovations, that would isolated or eliminate the guitar rhythm track in pre-recorded music.
It came out in the late 1990's it was a little black box (3"x4"x1") I used mine along with a 10 band graphic EQ and got pretty good results in eliminating or isolating the rhythm tracks.
It may or may not help in your situation, but I would imagine there are many used Rhythm Bandit units still around for very little money.
Bill