OK, I found it eventually. I'm not sure where "UI:Controls" are listed, but I did find the attrFieldSliderGrp so I'm getting close.

I'm have 2 problems now.

1.) How do I get rid of the texture button next to my slider? My command is:
attrFieldSliderGrp -label "Film Offset Horizontal" -min -1.0 -max 1.0 -at $xOffset;

I'm rtying to make a reset button that conrtols 3 variables, but I can't figure out the syntax. How do I get to to work for something like:
button -l "Reset Camera" "setAttr $xOffset 0, setAttr $yOffset 0, setAttr $overscan 1.2" ;

Thanks.
-dann