Rent a Tiffen 77mm Variable ND Filter at LensProToGo.com
Amazon.com : Freewell 77mm Threaded Hard Stop Variable ND Filter All Day 2 to 5 Stop & 6 to 9 Stop - 2Pack : Electronics
Amazon.com : NEEWER 77mm HD Variable ND Filter ND2-ND32 (1-5 Stops) No X Cross/Optical Glass/30 Layer Nano Coated/Ultra Slim Aluminum Alloy Frame/Water Repellent/Anti Scratch Adjustable Neutral Density Filter : Electronics
Fader Variable ND Filter Adjustable ND2 to ND400 Neutral Density for Camera Lens Adjustable ND2 To ND400 Neutral Density Camera Lens Fader Variable ND Filter 77mm - Walmart.com
ProMaster 77mm Digital HGX Variable ND Filter #9350 - Gene's Camera Store