Review on Think Tank 6197 Camera Rain Cover for DSLR & Mirrorless Cameras, Medium, 70-200 mm Lens - Ultimate Protection in Emergency Conditions by Timothy Louis

It may seem expensive, but it's far more reliable than a plastic bag and far cheaper than replacing expensive, supposedly weatherproof gear (you know what I'm talking about, Sony shooters). The medium size is great for a combination of Sony a7/a9 and 70-200mm lens (with lens hood). There's enough room to cover your hand and wrist, and enough slack in the material to use the zoom ring with ease. The hot shoe mount is a really smart feature as it keeps everything in place. Be sure to change FINDER/MONITOR to Monitor (Manual) as the cover sometimes highlights the EVF sensor and darkens the monitor screen. It is in MENU > CAM 2 > page 6 of 9 on a7 iii.