I'd almost rather it be the plastic type of trim...
If you have the missing piece, then you could silicone it back into place. This is possible because the fresh breaks would at least be clean glass, which adheres great to silicone.
If you try to remove the broken plate to replace it with a new one, you have to remove 100% of the silicone they used during assembly. If there's so much as a residue, the new silicone you use for the new brace will have its holding power compromised. NOT GOOD, and it's very hard for you to know for sure one way or another.
If you get lucky and the silicone comes off as one, solid chunk, that's about the only good outcome. If there's scraping and chemicals involved, I would not have any confidence.
Maybe look into whether there is a plastic top-frame that will fit this tank! :)