Hi,
Since those crash bars in the picture bolt into the same holes as for the engine mount bolts, I doubt that the ones for a 750 would mount to a 500/550. Ones for a 650 may, since the 650 and 550 use essentially the same block.
I just threw away a set for my 550, but the previous owner had tested the integrity of the crashbars with a right side slide down the road. The worst damage I found aside from lights being broken was that the crash bar had bent backwards and punched a hole through the clutch cover. It definately saved the engine cases.
Good luck,
Chris in Boston