I have been searching for just the right case to hold my Mavic Pro ND filters. I finally found what works for me which is the ThinkTank Photo “SD Pixel Pocket Rocket” SD card holder. It’s perfect for holding loads of ND filters.
This configuration allows you to hold up to nine ND filters.
I just used Avery Labels to identify the filter density so it’s easy for me to see which is which when I’m too excited out in the field! LOL