I have been making ND filters for the Phantom 3 and 4 but I don't have a Mavic Pro yet to get some measurements. If you will let me get some measurements I will make you a set of ND filters for free.
Here are some of the measurements I am looking for if anyone with a Mavic also has a digital caliper. I use metric but any accurate measurement will work.
A = Inner diameter
B = outer diameter
C = thickness of lens
D = gap
E = distance to gimbal
F = distance to gimbal