When a user rolls his mouse over the red balloon, the Paddy Caddy is highlighted and a button pops up to add the item to the cart. Slide over to the blue or yellow balloon and the Lamp or Radio respectively get highlighted.

The thought is to have an exploded parts diagram as your Category image. When a user rolls over a certain part on the image, that part will be highlighted on the list of items and the user can place it in the cart immediately.