I don't recall any shopping cart tutorials or SmartStarters.  But if you take a look at the shopping cart concept it is an exercise in data and state management.  That's a strength area of the K2 platform.  It is completely doable, you just have to decide the behavior you need and then build your SmartObjects and rules to create the result.

Hi Amy, 

You may want to have a look at the following list of smart starters we have available via the following link below:

https://www.k2.com/platform/pre-built-apps/smartstarters

But if these do not fit the mold which appears to be the case you may choose to reach out to our services team for further guidance via our website portal.k2.com.

Kind regards, 

Percy