Passing repeater values from one page to another is always a pain to set up and get working just the way you want. Check out the example on this thread on a possible way to do that.
But for an easier way to accomplish the same thing… you don’t have to put your shopping cart on a separate page. You could structure your site as a one-page web app and have the cart in its own hidden panel, and show it when the time is right, thereby avoiding the use of variables and complicated repeater shenanigans entirely.