I ordered  cheap filters from Ebay but they did noty fit my Phantom 4 Advanced camera. All kindly fully refunded, money returned in 1-2 days and no need to return the item. Excellent service in both cases.
These did not fit:
ND4/ND8/ND16/CPL/MCUV Lens Filter Kit for DJI Phantom 4 Advanced Drone Camera
Item ID: 173389389922
Seller ID: smilepower006

Filter Set For DJI Phantom 3 / Phantom 4 Professional, Advanced and Standard F7
Item ID:163014330460
Seller ID: lusomuch
There is still hope because the 3rd filter order from Ebay is still on it's way although ordered a month ago
Gold Wire Pattern HD Camera Filter Lens for DJI Phantom 4 Advanced/4 Pro+ Camera
( 371969674008 ), seller 2010ecshop.

In the end I ordered  the 4th set from Amazon.de. A reviewer confirmed perfect fit with 4 PRO. Parcel arrives on Monday (3 weeks from payment). I keep you updated.
Anbee Pack of 5) Camera Lens Filter UV CPL ND4 ND8 ND16 for DJI Quadcopter Phantom 4 Pro/Advanced UV CPL ND Filter Neutral
Sold by: Amazon EU S.a.r.L.

No fit with Phantom [url=https://drive.google.com/open?id=1l4XVInd1M4qlAYJ4UARF0Ieo0o5NxP01qg]No fit with Phantom 4 ADV+4 ADV+[/url]

Hello there. We apologize for the inconvenience. Good thing you were able to return it and have a refund. You may also check in our store: https://store.dji.com/product-se ... 20advanced%20filter

Update to my post 8-3 19:14. I complained about slow delivery (5 weeks, expected late September - erly October)  2010ecshop. They promised to send a new one for free. But today I received the ND32 filters which looks good and fits perfectly to my Phantom 4 Advanced+.

Quick update to my post 8-3 19:14: seller 2010ecshop promised to send a new filter for free if not arrived in 6 weeks from payment. But the ND32 filter arrived today and fits pefectly

Update to 8-3 19:14 filter set ordered from Amazon.de (Anbee Pack of 5) Camera Lens Filter UV CPL ND4 ND8 ND16 for DJI Quadcopter Phantom 4 Pro/Advanced ) was sent 20th of July and arrived Helsinki 27th July. No tracking updates since. Complained to Amazon. Quick reply with appolozises with & free express delivery (value 13.or a reorder. It is on its way 2 days after my 1st email to Amazon.