If you try to glue this back together you're just going to end up with a mess.
What I might do, while you're pondering what to do long term, is consider drilling a small (1/8th of an inch or less) hole at the end of the crack to keep it from progressing.
I'm guessing the enclosure is a gel coated fiberglass, also commonly used in bathtubs and residential shower enclosures. These can be successfully repaired and if done by a qualified and experienced tech you'll be hard pressed to find the repair after the fact. Some of the larger boat yards may be able to do the repair too.
Of course this could be seen as an opportunity to rip the current enclosure out and have it replaced with a tile shower enclosure. I'm sure that won't cost much more than this years travel allowance.