You can create your own product pages and use the 1&1 eShop's cart integration.
The item properties (item number, price, name etc) are added to the cart in a
hidden form field. You can add any number of item attributes, such as colours, sizes
etc. Logical associations between item attributes can be displayed with PHP scripts.
Because of high amount of programming required, cart/basket integration is really
only suitable for a fairly small range of products with rarely any changes. Because
the shop's session management cannot be used, the shop needs cookies in order to
differentiate between various shopper's baskets. The eShop's Product Search feature
cannot be used too.
Basket/Cart integration is ideal if you already have web pages displaying your
products and just want to add a basket function.