Intrepid '99 Rattle in Rear

My '99 Intrepid has had a steadily growing rattle in the rear of the
car. The last time I had the car to an independent mechanic, he said it
was coming from the muffler baffles and that it would be more cost
effective to wait until the exhaust system needs work before doing
something.

The rattle happens on the smallest of bumps and sounds like it is coming
from the right rear side, not where the muffler/resonators are.

The last time I had the car raised for an oil change I looked at the
anti-sway bars, they are rusty but appeared sturdy. I couldn't make
anything rattle.

Has anyone experienced this in an LH car? I'm changing my oil this
week, what should I look for?

Thanks!
Greg