cross-site, or multi-domain mini cart question

[Ron]

Hi all,

I know that the mini cart uses cookies to store the customer's cart contents, but I have multiple stores, each with its own unique domain name, and they all funnel into the same shopping cart on one dedicated domain specific to the cart. As such, the mini cart is essentially useless to me as it's implemented.

Here's my question - does anyone know of a way to use Javascript to make the mini-cart usable across multiple domain names? Perhaps an image that "explodes" to display the cart contents when rolled-over (similar to how many of the security seals on the web work)? I imagine that the JS source and image could be hosted on the cart's domain.

For instance, at http://www.pair.com/services/e-commerce/pairssl/
There's a security image near the bottom of the page. Roll over it to see the SSL certificate data. The JS and the image source are all on different domains.

Another idea - perhaps use the PHP gd library to turn the cart into an image- as in: img src=http://www.mycartdomain.com/minicart.php/timestamp
The timestamp will insure that the "image" is not cached by the browser, but I'm not sure if all browsers will transmit cookies over an image link nor how to add the timestamp to an image tag within the body of the cart itself.

I tried an iframe a while back and had lots and lots of compatibility problems across browsers. It mostly worked, but not reliably, and I eventually gave up.

Any ideas, source, technical resources, compatibility tricks or other information would be greatly appreciated.