I found the a DJI phantom lens screen protector for $8.09 on Amazon, after 10% off.
Coupon Code: M7YXCO4W
$8.99 - 10% off=$8.09
Code expired after 31'Oct 2016
Kuuqa Camera Lens Screen Film Protector for DJI Phantom 4/3 :
It is a film attached to your lens to Protect optical coating film of the original expensive lens from dust, scratches, fingerprint, made with high transmittance transparent ultra-thin crystal glass.
1 x Kuuqa Lens Screen Protector
This seller also provide in-store promotion, you can have 5% off on all you order if you purchase two or more items from the seller, no additional code required.