I am based in the United States, so you get all the benefits of time zone, communication, and availability that results in. (I previously worked with a client based in Toronto for a couple of years, and we had a great working relationship where we met at least once a week via Skype). If you award me the project, you'll have access to me to communicate on the project as you need.
I have been building web applications since 1999 using almost every language. These days I specialize in Ruby on Rails, which is ideal for Shopify, since they are one of the largest Ruby on Rails applications and they publish their libraries in Ruby first.
I have experience building add-ons for Shopify. I built the add-on for Refund Retriever, integrating their service with the Shopify interface and authentication workflow. (I've also built add-ons for other platforms: Magento, Bigcommerce, and WooCommerce)
I can get started on this right away. I'm available today and this weekend to discuss this if you would like.