I built on sabithpocker's idea and made a more generalized version that lets you control more than one selectbox from a given trigger.
I assigned the selectboxes I wanted to be controlled the classname "switchable," and cloned them all like this:
$j(this).data('options',$j('select.switchable option').clone());
and used a specific naming convention for the switchable selects, which could also translate into classes. In my case, "category" and "issuer" were the select names, and "category_2" and "issuer_1" the class names.
Then I ran an $.each on the select.switchable groups, after making a copy of $(this) for use inside the function:
var that = this;
$j("select.switchable").each(function() {
var thisname = $j(this).attr('name');
var theseoptions = $j(that).data('options').filter( '.' + thisname + '_' + id );
$j(this).html(theseoptions);
});
By using a classname on the ones you want to control, the function will safely ignore other selects elsewhere on the page (such as the last one in the example on Fiddle).
Here's a Fiddle with the complete code: