For a while I have used a small foldable umbrella to cover the camera during rain. Even though the weather proofing is often decent you definitely want to avoid water spots on your lens. This is especially difficult when using square filters since you cannot use a lens hood with the filters. Holding an umbrella in your hand is not ideal though.
In 2017, I bought a Versa-Brella with built-in clamp. It worked OK but was difficult to connect to thick heavy-duty tripod legs. The clamp failed me once during a rainstorm and it was no fun finding the screws on the ground. It is also not a good umbrella to use as a regular umbrella.
At the beginning of the year, I tried to come up with a different solution for an upcoming winter trip to Yosemite National Park. I looked for umbrella clamps all over Amazon but did not see anything worth buying. I used a variety of search terms and eventually found a “Heavy Duty Dual C/U Clamp”. It was not advertised as an umbrella clamp but looked like it should work and was not too expensive.
Two days later, I received the item and connected it to my tripod. It worked just perfect. You have to have a center column in order to use it. The center column needs to be raised just enough for the clamp to fit under the ball head. It is solid metal construction and very secure. It even opened wide enough to hold the handle of my foldable umbrella and you can tilt it forward and backward.
Update June 2019: The item on Amazon got changed to a different product. I am not sure if this is temporary or not. Since I am unable to locate the clamp on Amazon at the moment, here are two eBay links that might help. Just be sure to not get the double clamp with a fixed right angle or the umbrella will be useless.
If you do not have a folding umbrella I would suggest one with 9 spokes. It will last better with wind or under snow. They are not too expensive either. I have the following umbrella..
This setup worked really well in Yosemite National Park during snowfall and I am sure it will see a lot of use in the upcoming years.