In my case there was quite a bit of damage to the housing that was not only visible, but also would allow things like sand and pocket lint into the device internals.

To address this, I mixed up a small amount of modeling epoxy and filled in those spots after the seam adhesive had set fully. Then I took a medium grit piece of sandpaper and smoothed out the surface of the epoxy. Finally I used a very high grit piece of sandpaper to blend the plastic surface in with the filler epoxy.

This strategy didn't result in a perfect finish (this picture is a stock photo used purely as a reference) but I am confident that on a technical level it has been restored to the same level of protection for internal components.