How to change the variant picker to a button that opens a sidebar in the 'Distinctive' Shopify theme

[tomkingham]

How in the 'Distinctive' Shopify theme can I change it to make the product variant picker a button that opens a sidebar for choosing variants like engraving?

This is the site I'm working on, and as you can see, the 'Variant Picker' sits on the product page. I want it to be a button like on the Missoma page that, once clicked, opens a sidebar for choosing the variant.

Missoma product page
My site