I have a set of 3 Polarpro filters plus case and box, only used a few times. Filters are ND4, ND8 and Polariser. I live in the UK. I got them for a Phantom 3 Advanced, so not sure if they fit a P4.
I've never sold anything on this site before, so you'll have to tell me how to go about it if you're interested (for instance, I don't know how to send a private message to another user).