Shopify TCG Store Enhancement & Completion

Looking to have my shopify store finished off, and also implement a new feature. It's a tcg store and I am looking to have a feature where the customer will be able to make a list of the cards, and it will check my store/inventory and will add the cards in stock into the customers basket... (Budget: £20 - £250 GBP, Jobs: API Integration, HTML, Inventory Management, Shopify, Shopify Development, Shopify Templates, Web Development, Website Design)