Raincoat while wearing external carrier?

My department recently authorized external load bearing vests but won't let us wear any jackets or rain coats underneath. Does anyone have any recommendations on raincoats that can work with an external vest carrier? I have a hooded jacket but during heavier rain, it just gets soaked and it's only Ike length.

I used to wear a PVC coated raincoat that would zip and snap up. It was long enough to go to my shins and would always keep me nice and dry. I tried buying a larger raincoat but I look like a bowling ball with the arms of an inflatable tube man.