Found this: https://discourse.roots.io/t/using-bedrock-composer-with-premium-plugins-w-no-repo-or-source/2731
And sounds like it’s a common issue with no perfect solution, as I can create my own composer package for each premium one but then would have to manually update that each time there is an update to the plugin which would seem to be far more work that what composer is suppose to be saving. The other being to allow those specific plugins in git which seems be the best option until premium plugins (Gravity Forms in particular) are on composer.
Thanks!