See if you can find a plastics shop nearby that will sell you some Methylene Dichloride.
When I was in college, we use to build our architecture models in plexiglass and used the Methylene Dichloride ... it was sold to me in an old cough-syrup looking bottle - flask shaped, brown glass, complete with a skull and crossbones sticker on it and a POISON label. Was kinda funny bringing a date into my dorm room when that bottle was left out ...
Anyway, brush it on both pieces quickly, press them together. You're essentially solvent welding the two pieces together ... and, if done properly, your solvent weld will be stronger than the actual plexi ...
It won't take away the line - but it will make your piece one whole ...
Another ugly solution we use to do with cracked plastics on our dirtbike fenders was to drill several small holes up and down each side of the split and use wire to frankenstein stitch that piece up ...
