You need to - as you tried - modify it using CSS. Perhaps you are not applying CSS change to the element you need, you need to apply it to .jqplot-event-canvas :
$('#chart1').on('jqplotDataHighlight', function () {
$('.jqplot-event-canvas').css( 'cursor', 'pointer' );
});
See working example here
Change . Script and code updated according to sdespont comment .
PS As written by Lucas Jelinek, you can override the default pointer when you dispute your data:
$('#chart1').on('jqplotDataUnhighlight', function() {
$('.jqplot-event-canvas').css('cursor', 'auto');
});