I need some custom configurations for my shopify site

I have set up a shopify store but I need some custom product configurations

I want to have a separate button, underneath the "Buy it now' button which will be name "Add sample"

This button will add a "sample" of the product to the cart. The sample product will have a different price, and currently I have it set up as a product variant.

Similar to how this site works : https://www.janeclayton.co.uk/product/sweetchestnut/142435

I am currently using the "Minimal" theme on shopify. I have attached a screenshot of the current product page. (I do not want to show the "sample" product in the Size dropdown, like it shows currently)

Please let me know if you need anything else from me at this stage in order to provide a quote.

Thanks alot,

Hassan