Where are P4P Adjustable ND Filters from?

[KurtJensen]

Sure I've seen an adjustable ND filter for a P4P but cannot locate them.
Would love to get these instead of buying individual ones.

 

[KayJay]

Selens Pro ND2-400 Variable Neutral Density Filter Lens For DJI Phantom 3 4 | eBay

I wanted one but don't suit the P3s

 

[msinger]

I wanted one but don't suit the P3s

Freewell makes an adjustable P3S filter. You can find it here.