I'm not aware of any way that a shop could integrate any payment gateway that they want, it would have to be a gateway that had a pre-existing integration with Shopify. In order for payment gateways to integrate with Shopify currently, it must be done via our Hosted Payment SDK.
Have you checked the Shopify admin to see if they already have an existing integration, or contacted the gateway provider directly?
No, it is not available in the admin and there is no app in the app store for using it. I've spoken with Behalf and they would create a custom integration for us only if we were Shopify Plus customers. Unfortunately, we are not at an enterprise level yet.
Are we free to redirect interested customers to our own portal to handle such payments? Since Behalf has an API, we can construct our own integration, it just wouldn't pass through Shopify's checkout. We'd then simply create manual orders in Shopify after handling the transactions on our own servers. I was hoping there would be some existing mechanism for this, but we are prepared to go through the route of constructing a workaround.
Hey again @Josh_Davis1 ,
That's really unfortunate - there are gateways not available in the admin that are still on Shopify, which was why I had suggested asking the gateway directly. There is a threshold of sales/installs that needs to be met before a gateway can be listed in the Shopify admin for all merchants, so until that is reached there are some gateways that need to send an install link manually.
If you find a way to integrate them externally you're free to do so, however we wouldn't be able to support you through the process.