I just finished adapting the plugin for Kirby 2.
You can test the demo here: http://cartkit.dsply.fr/
And even clone the github repo:
git clone --recursive https://github.com/dsply/cartkit.git
link repo: https://github.com/dsply/cartkit
It remains to put the links in ajax ( + / - / x ).
Maybe also add Tax.
This is perfect for a small shop.
Cart blueprint :
Product blueprint :