How to implement a simple shopping cart without Commerce and Ubercart?
The Basic cart module is the best solution for you...


  Basic cart is a very simple shopping cart / checkout process for
  Drupal, that just sends 2 emails after each order. Along with the
  shopping cart, this module also provides a block where you can view
  your cart's content. It's ideal for small websites with only a few
  products or other content types being sold, for example touristic
  offers.