Josh, try here:
S&W Race Cars . That's where I got my 6-point cage from. Look
here or
here for pics of it in my car. They sell the swing out kit for the cage. Their mild steel cages can easily be MIG-welded unlike the more expensive chromoly cages (which are a tad lighter in weight and need TIG welding). S&W also provides 6-steel 6"x6"x1/8" plates.
Just for the record, NHRA rules state that any convertible street car running 13.99 or quicker must have at least a 5-point cage (main hoop-2 points, back bars-2 points and driver's side diagonal bar-one point). (Cross bar that goes between main hoop does not count as "points"-- "Points" are only where roll cage is welded/bolted to floor). And the driver's side swing out bar is permitted. If not convertible, then at least a 5-point cage (same as above) for 11.99 or quicker. (plus what Mustangbelle already mentioned) But then again, you didn't ask all that, you just want a 4-point cage, sorry, don't know about where to get those
