Since you don't actually need very detailed maps -- the hexagons are large, zooming in is pointless -- and your dynamic data is a simple overlay, I think you should be able to use static tiles generated just once. And you should be able to generate the tiles from free OpenStreetMap data, the country outlines & major cities there are plenty good enough for this use, even globally.

Yes, I know it's not as simple to throw together as just using Mapbox.