OK, I see. In your case, you can write a mod that will create a piece of JS code that sends a request to X-Cart 5 core (via AJAX), pull customer's cart and then generate the cart widget that can be placed anywhere.
It will require some knowledge of JS and PHP as it will be quite complex task, but if you want to create it yourself, I will try to help you. Otherwise, you can order a paid modification from our techs:
http://www.x-cart.com/contact-us.html