I use one of the free themes "Refresh". On the product page there is an add-to-cart button, and a buy-now button. Using the "Custom Liquid" block on theme editor, I want to add a 3rd button with "Buy on Amazon" that links to the Amazon listing of that product.
I forgot to mention that I used "button", "button--secondary", and "button--primary" as well but those came in too short (shorter than the other two buttons). As of this moment, I adjusted css style so that all buttons are full-width. But I prefer to find a way to match the original width shown in the original post's screenshot.