Rider> Thanks, I didn't even realize I had seen that on this site...
As to worries about breaking, glass is stronger then we tend to think it is. The sharp edges are a concern, but it just takes a few passes with a sanding block to take the edge off - more if you want a nice squared or polished edge, but if safety is a concern, it doesn't take much.
You should easily be able to get a piece of glass that will fit in that slot in your trim, and cutting off the corners would be quite easy. not sure about the part in front - someone skilled in cutting glass could probably do it, but I don't think I could.
It looks like the slot is thick enough you might be able to fit two pieces in there, if you wanted to slide the top one back a bit for access to the tank.