Wow. If I could sketch out my idea, I think it would be easier to understand but I'll try to explain how I would try to line that hole up:
I would start with a 2x4 or 4x4 block of wood. Next I would cut a square notch in it such that it would rest completely against the rollbar (Rollbar in the notch). Once I have that cut, I would take it to a drill press to drill straight through it so I could run a drill bit through either direction. With this device, I would then have a drill jig that I could run a hand drill through. If you make this device wide enough, you could drill both the holes that correspond to your handle attach point at the same time and (provided you measured the distance between the attach legs correctly) it would be dead-on.
I would likely start by drilling the holes 3/32" and enlarging as necessary. Even using this jig to "nick" the front and back of the roll bar will give you an accurate location to drill holes with after removing the jig.
The angle at which the handles attach the rollbar would be a concern but the jig could be rotated on the rollbar until you find an angle that is ideal (although, if you're not careful, they might be different from one handle to the other).
Another method might be to measure the circumference of the rollbar. Drill the front hole (where the handle will exit)...exactly half way around would be 180 degrees from the "IN" (where screws would attach handles. Drill both sides separately (and start small). Enlarge as needed.
I hope these ideas help you come up with a workable plan. (I think the second might be easier than the first but it didn't come to me until after I thought about it.)
Good luck!