The method Yehuda described is the best one.
The SKU object representing Product data is separate from the TreeNode (Page) object. This means that it is perfectly possible to use it in the E-commerce module without the associated Page. In fact, once the Product is added to the Kentico Shopping Cart, only the SKU is used from that point forward. The relation to the actual Page is forgotten.
This means that to achieve your goal you will need to write your own web part that will present and customize the added product according to your needs. To add the item to shopping cart use code similar to method AddProductToShoppingCart from the ShoppingCartItemSelector control.
First, create a new instance of ShoppingCartItemParameters object and fill it with information about what item (SKUID), units and Product options (SKUIDs) should be added to the shopping cart. Afterwards, generate ShoppingCartItemInfo object using method ShoppingCart.SetShoppingCartItem(ShoppingCartItemParameters itemParams). And finally, save this new object to database using ShoppingCartItemInfoProvider.SetShoppingCartItemInfo(ShoppingCartItemInfo itemObj) method.
I recommend checking the code of the AddProductToShoppingCart method. Once you see it, it should be clear how an item is added to the Kentico Shopping Cart.