But I'm thinking … maps.
Unfortunately, the paper in all the available offerings is lightweight and probably won't hold marker pigment well, let alone paint. (The big-sheeted dry-erase grids intended specifically for games look like a lot of fun, but aren't what I'm looking for) Is there, to the best of your knowledge, a hexagonal notebook with paper that's 100gm or more?
Watercolor paper would be ideal, but I'm not fussy.
PREVIOUSLY: Create and print custom gridded paper