I think I remember, Eran Stern used to offer a lot of green screen stock footage of actors doing different things, I think it was called Crowd Control or something, but I can’t remember if he had anything like stunt people being flung into the air on green screen. Typically, for a project that specialized, the specific circumstances of the shoot would make it hard for stock imagery to work. I think most producers would have this shot to order in a custom setup.
But, there is one other way you can do this that’s inexpensive in terms of money but may cost you in terms of time. that would be to generate the bodies in a 3-D CGI application like Poser or Maya, or lightwave, and use the built-in physics and invese kinematics of those programs, to generate realistically flying and falling people, in all shapes and sizes. The next step would be to composite those generated virtual stuntmen into your fake explosion.