There is a tiny little pin that rests in a spring loaded recess below the cover at the top of the camera.

When your cover snapped off, that pin was lost.

I have an XA with the pin missing and I have to hold the cover open by hand to work the camera.

I think if I find a stainless nail or brad of the correct thickness (thin-ness?) that I can cut off a piece and make it work as a replacement.

Just for the record -- there is a barrel-shaped "roller" that goes in a rectangular opening between the top cover and the sliding "clam shell" lens cover. You can fabricate a replacement for the missing stainless steel part using a short length of round brass stock from a hobby shop or the like.

Remove the bottom cover (5 screws) and lift the sliding cover out from the bottom to remove it. Get a piece of brass rod approximately the same width as the rectangular opening and snip off a small piece to fit. Lay it in the opening and replace the sliding cover and bottom -- should be good as new.