When you create a new product, we will instantly generate an embeddable buy button for you which can be found in the "Embed this product" tab.
Here is an example of a Shoprocket site using simple buy buttons. As you can see, there is no sr-block as there would be normally, but instead a sr-add with the ID number of that product.
Of course, your code snippet can be modified slightly. By default, the link will say Buy, but you can change this text to whatever you like, such as Buy now, as seen below.