Water Repellent Solution For Camera Front Cover Lens?

Due to heavy rain recently in Europe, customer’s camera is covered with raindrops and they couldn’t see image clearly. (Water didn’t come inside the cameras.) So I was wondering is there any water repellent solution for this situation without affecting video/optical quality?

Is something like Rain-x suitable?

Rain-X is typically mentioned, but be wary of the reapplication intervals. This thread mentions a product used on racing windscreens that a member recommended:

Prevent Salt Water Mist Build-Up On Dome?

There are also specific cameras that often come treated with a hydrophobic coating. We talked about two of them here:

Panasonic Rain Wash Coating

DW CleanView

A long time ago on LinkedIn someone swore by using Aviation windshield water repellent, was something like $25 dollars a bottle or something. Sorry I don't remember the brand they mentioned.