Customise Shopify plugin Bundle Builder

On our Shopify website [login to view URL], we use the app Bundle Builder by Agile to offer several product bundles to customers. Need a small customisation to the template of this plugin. Once a customer customises a bundle, they get the option to Add to Cart, after which they can check out. Now, we want our customers to directly Check Out using the hosted payment page of an external payment provider (Zoho), rather than adding the bundle to cart. We will do this through unique Buy Now buttons created by Zoho for each bundle. Currently the Bundle Builder app has no option to modify the Add to Cart button for each bundle. We would like to customise the app dashboard to add an option like the one shown in the attached jpeg, so we can replace the Add To Cart button with a Buy Now button with a unique hyperlink for each bundle. Please bid only if you have experience with customising Shopify plugins and payment integration.