Those are to protect the forks, which your gaiters are doing, so you can pop them off. The Yamaha optional gaiters require removal of the guards.I just fitted mine, they were from S2 Concepts and cost about €40,-
I guess you could go on Amazon/Ali to get some generic ones, I believe you need a 42mm diameter and you should be fine.
By the way my forks have the optional guard-thingies sticking out of them, your gaiters will not fit over them so the bottom end will be hanging freely. I'm still looking into a solution for that, I don't know if these guards can be removed, they seemed to be sitting pretty snugly around the forks so I didn't try and pry them off.