Can you find Fischer's ...19 Bg4 !!

[Dr.Ex]

I very much doubt that Fischer's 19...Bg4 is winning the game.
A critical position is the following:

[D]r3r1k1/pp1q1p2/2p2npb/PPPp4/3PpN2/2N1PpP1/1R1B1P1K/3Q3R w - - 0 23

and here White should perhaps have played 21.Nh3 to avoid
Black's Bxf4 allowing to open the h-file with tempo.

Regards
Kurt

You mean 23.Nh3. Have you really considered the Idea of Fischer? It was Kg7,Rh8,Rh7,Rah8 and maybe Qg4.