I have a Black 1996 Tracker with a black drop top. I live in the Florida Keys where it is often 90f and humid. I also tend to wind up in places like Death Valley in August.  The AC would be adequate in most places but here where the sun literally strips paint, it can't keep up. Because of the sun on that black top I can't get the temp inside much under 90f many days. The AC system is putting out all that it can but....1996! I gave it a thorough going over and it is up to specs. I can feel the heat from the top and it pools in the back. I hear my wife whining too I did discover that I could cut the heat by moving the recirculate slider just a tiny bit towards fresh air to blow some heat out of the back Not too much because of the 80% humidity though. I also used some very high tech window coating on the side windows that stops heat but not much light. I know a new, light colored top would help but if I had a thousand dollars I'd raise it and change the tires .
  Most convertible tops have some padding or more than one layer and this does not. I wondered if there is something that could be attached to the underside of the top to reflect or block the heat but not be too ugly. Having the top that slides open could make that tricky. Has anyone done it?

I have read about people building ones out of Thinsulate for Jeeps for extra insulation. Could probably do something similar if you had access to someone who could sew.