Development of JavaScript enabled buttons within existing website

We have an existing website fully built out on the [login to view URL] platform. We are having a problem integrating a javascript a href with their pre-defined css for buttons. The javascript is for integration with our payment portal (Chargebee) which populates the payment window as a pop-up without leaving the site. We either need a workaround on the current CSS or a new custom styling for the javascript links to look identical to other buttons on the site. (Right now it only works as an un-stylized link) Site is built on [login to view URL] platform with full developer html/css access and on the ZURB Foundation framework for front-end responsiveness.