Sure they do. Go to a Walmart and look in kitchen wares; look at the small plastic bowls and storage containers. You'll find round ones just the right size. Just clean it with dish detergent or alcohol and paint it an appropriate color.

A club member also used a round cashew can. You know the ones, with a tin bottom and lip at the top, the rest is cardboard. Once it was painted and mounted, you couldn't tell it wasn't made for the plane.

Experimentation and ingenuity is what makes this hobby great. Go try something!
Dennis-