THIRD PARTY PAYMENT FOR A PHARMACY

I am trying to setup an online pharmacy in Australia with a shopify site. I meet all my regulatory requirements for a pharmacy and have all the documentation. I am struggling to find a a payment gateway on the Shopify third party list that will support my business. I currently have found a payment gateway, Till Payments, however they are not listed on the Shopify payment list. Is there a way they can be listed or the checkout can be directed to a Till payment page?