Cost effective way to finish this shower?
IMO, not really (someone screwed the pooch with that mirror). TL;DR: it's curtains for you, or bust ($$$).

If I had to guess, any type of custom shower door is going to cost $1~2k installed. So, you should get some estimates and see where you're at. If they all want 2.5k for glazed doors, why not go all the way and get what you want? Perhaps one of them will do some sort of financing?

Take some really good measurements; you might be able to squeeze a complete door set behind that half wall, to make this a feasible DiY project (but that will probably lead to a mold problem).

ATM, my town is in "construction season" (summer); wait for winter to come around and everyone's prices should drop. Use a curtain in the meantime, or at least until you can secure a reasonable bid.



As I understand it, cutting tempered glass is basically out of the question. So this is either going to be full-on custom, or ad-hoc schlock. You've literally backed yourself into a corner here. (who put that mirror in?)

DiY - cut tempered glass, "Step 2 - Anneal the Glass"

Good luck with that!... I sincerely doubt you have a 6' oven.



There are several different types of corner shower doors that come as kits. Using 2 out of the three panels (and a small filler strip of 'C' channel if necessary) might do the trick, but you'd better measure everything extremely well...

Good luck in your search, these days "adjustable" means it can be ever so slightly out of plumb, and still hang frameless doors. To the best of my knowledge, no one sells a glass door with actually 'adjustable' (non-glass) side panels but someone might. 



I have seen accordion style (folding) plastic (PVC) shower doors; the hard part is going to be finding one that has a track that will fit your angled base, and then you would 'simply' cut it to size. Or just get a straight one and modify it.