Google Analytics Goal Tracking

I have a project (which has multiple products) for which I am setting goals to track conversions (the trigger for each conversion being the SALE of each of the products) ; but the issue is that I cannot use the URL method as the final url that is generated after each sale is done is the same no matter which of the products the customer buys and although I can track the sale in general; I cannot track the sale of each of the products (which is what I want to do) So basically, I am looking for someone who can help me set up the goal tracking on google analytics with the above mentioned constraint (I am not sure if it's even a constraint per se - might be something very straightforward)