Multiple servers and on premise gateways

Ive been looking all over the web for a few days and havent been able to get a clear idea on this:

I have two seperate SQL servers at two seperate sites with seperate networks. I need to use them both in one data model.
I have an on premise gateway installed at each location.
I can only choose one of the gateways for my model in Power BI service.

What is the best way to deal with a scenario like this where you need to add data from two seperate SQL servers from seperate networks at seperate locations to one data model?

Cheers