Add jQuery popup on Shopify theme

We need a custom feature added to an existing shopify theme. We need a jQuery popup dialog when a user enters the website. The user will be asked to enter their postcode/suburb with auto-predict like http://www.deliveryhero.com.au. If their postcode/suburb matches a list of authorised postcodes/suburbs then the user will be able to proceed to the website. If not they will be displayed a message saying, sorry we don't delivery to you and a button to 'browse anyway'.