Adding external url as item for commerce site

Hi All,

My wife has an online cliass hosted with Thinkific. She has been working hard to design her first site with squarespace and has an online store as a part of the site. She has a url to her Thinkific site and would like for that to be available to customers when they purchase an item on the Squarespace site.  Is anyone able to provide a solution for this? Thanks

You want to click add to cart on individual products >> Redirect to Thinkific? You can add a Text link in Description, then we can give code to remove add to cart & change text link to button style

Or you want to click button on Product List Page >> redirect to Thinkific site? 

I believe she was able to figure out the button on product list to redirect to Thinkific.  What she would prefer is to have them add the class to cart on her site and then when "purchased" (no actual cost because that's processed on the Thinkific site), it would show them the link to thinkific and send them an email with that link. Is this possible?