Assuming it's fiberglass, you can clean it up, use automotive body filler like "Bondo" and then sand it smooth and paint with acrylic spray paint.
This technique is used on fiberglass tubs and shower stalls in homes.
Basic issue is matching the color.
A possibility is a tub and shower refinishing outfit if you don't want to do it yourself.
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'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Radios inside and many antennae sprouting from roof, ProPride hitch
2012 shortbed crewcab 4x4 Toyota Taco TV with more antennae on it