Gotcha, all I noticed was "stainless" which is associated with steel, not aluminum. Skipped right over the aluminum after I saw the word stainless. Just over 210 with the a/c on is perfectly normal and right where it should be. In fact, 210 without the a/c on is perfectly normal too, that is where Jeep designed it to run at.
You can't really get a better cooling radiator than the factory installed all-aluminum core radiator and since your TJ's temperature is right where it should be, I wouldn't worry about it at all.
There are aftermarket radiator manufacturers that make custom all alumium radiators but they are generally $400-500 and more but you really wouldn't notice much difference in your engine's temp.