Multiple navMeshes? (swapping navMeshs at runtime)

here is my scenario: i have a set of small levels (multiplayer brawler style) which are stored as prefab assets. during runtime, the game initialises one of the prefabs based on what level has been chosen. this all worked well and good (in fact not needing to switch scenes constantly was a big bonus), but now that i need to use navMeshes there is a problem.

ive got everything working with one level (baked the navMesh, bots follow it, etc...) but i now need to find a way of making navMeshes for ALL of the levels, and then store them. then the correct navMesh could be initialised along with the level prefab.

although turns out navMeshes don't seem to work that way... ive looked around for a while now and can't seem to find a way around this.

so, is there a way to store multiple navMeshes as assets? or will i need to find and alternative way of doing this?

any answers/advice will be greatly appreciated.