Procedural meshes, saving as prefabs

I'm working on a game with a hex grid. I'm currently spawning a bunch of hexes (using ECS) that I modelled in Blender and saved as a Prefab. So I'm using a Prefab as a way to instantiate a lot of Entities. That works great.

However, that means if I ever want to change my hex tile (make it bigger/taller/whatever) I need to make changes to the .fbx file and then to all the code that might depend on its size. I'd like to generate that hex by code. I've done that before, but I never needed/wanted to save it as a Prefab later.

Any ideas?