I work as a welder and used a #14 lens to watch the transit of Venus a few years ago. It's much darker than a normal welding lens so any old welding shield will let through too much light, gotta get the right lens. Any decent welding shop should have one for 5$ and then you can make a cardboard welding shield. I would buy a bigger 4x5 lens for more viewing area but depends on the selection at the shop.

The easier thing to do is just buy eclipse glasses if you are watching with friends this seems to be the way to go.