The one in the link is just a tent. It might also need a gap to see through. It's going to get hard to see if the water just runs down.

An umbrella of some kind clamped somewhere on the bike would be simpler. But umbrellas tend to be airfoils and then become parachutes. You may not notice it if you are used to using one, or may not have the knack if you don't, but you tune the pitch of an umbrella to zero lift. You can't do that if it's clamped to the bike and you are spending your attention steering. So maybe add the vents like a patio or beach umbrella. But then is it watertight? hm

google?