I need to integrate a third-party payment to Squarespace?

Site URL: http://araraswim.nl/TEST

Hello,

I am using Stripe for my payments in Squarespace but I need to use a payment method on my website that is supported by Stripe but not by Squarespace. I tried integrating shopify Lite to use my Squarespace with the Shopify add to cart button, but the product page looks very weird. I also can't add more details or more than one photo about the product since customers have to add the products to cart on the product grid page.

Is there any way to only add the Shopify (or other third party) button to a Squarespace product detail page? (thus not changing the product pages, only the button itself?)

Thank you