If you're wanting to do just you two, your best bet is to port forward again sadly.
If you're willing to have other players in your game (but on your team!), I can highly recommend the Flashpoint Levant and Grayflag servers.
Technically speaking you can get a dedicated server from providers like Fox3MS, but I don't think that's very reasonable for what you're getting up to, with their lowest price point being $43/month.
There's plenty of guides on how to port forward, and you should just need to open up port 10308!
Czechnology's post in Would Like to Play With My Friend Both of Us have F-4E - Connection Question was marked as the answer