Select tags that starts with "x-" in jQuery

How can I select nodes that begin with a "x-" tag name, here is an hierarchy DOM tree example:

<div>
  <x-tab>
    <div></div>
    <div>
      <x-map></x-map>
    </div>
  </x-tab>
</div>
<x-footer></x-footer>

jQuery does not allow me to query $('x-*'), is there any way that I could achieve this?

There is no native way to do this, it has worst performance, so, just do it yourself.

Example:

var results = $("div").find("*").filter(function(){
    return /^x\-/i.test(this.nodeName);
});

Full example:

http://jsfiddle.net/6b8YY/3/

Notes: (Updated, see comments)

If you are wondering why I use this way for checking tag name, see:
JavaScript: case-insensitive search
and see comments as well.

Also, if you are wondering about the find method instead of adding to selector, since selectors are matched from right not from left, it may be better to separate the selector. I could also do this:
$("*", $("div")). Preferably though instead of just div add an ID or something to it so that parent match is quick.

In the comments you'll find a proof that it's not faster. This applies to very simple documents though I believe, where the cost of creating a jQuery object is higher than the cost of searching all DOM elements. In realistic page sizes though this will not be the case.

Update:

I also really like Teifi's answer. You can do it in one place and then reuse it everywhere. For example, let me mix my way with his:

// In some shared libraries location:
$.extend($.expr[':'], {
    x : function(e) {
            return /^x\-/i.test(this.nodeName);
    }
});

// Then you can use it like:
$(function(){
    // One way
    var results = $("div").find(":x");

    // But even nicer, you can mix with other selectors
    //    Say you want to get <a> tags directly inside x-* tags inside <section>
    var anchors = $("section :x > a");

    // Another example to show the power, say using a class name with it:
    var highlightedResults = $(":x.highlight");
    // Note I made the CSS class right most to be matched first for speed
});

It's the same performance hit, but more convenient API.