suggestions from remodelers for an unusual bathroom ceiling situation?

I'm remodeling a funky old utilitarian bathroom to make it pleasant, attractive and comfortable for the guest suite we are installing in the walk-out part of the basement. The old bath just had painted concrete floors (I have poured floor leveler and will be installing ceramic tile), the walls were cheap plastic panelling (I have removed that, furred them out and will use green board above and hardi-board and tile below). I added a vented glass block window, an exhaust fan and new wiring and plumbing. It will have a large tile shower.

My dilemma is the ceiling. The overhead area in the bathroom proper is 7' 6" x 5' and in the adjacent shower will be 42" x 72". The ceiling throughout is currently exposed 3/4" styrofoam insulation glued directly to cast in place concrete (the bathroom is under a concrete porch). I have limited headroom in here -- it is barely 86" as it is, so I really can't afford to fur or stud the ceiling (which I could do with a hammer drill and concrete fasteners). Is there any fairly economical and lightweight sheathing that I could glue to the styrofoam instead? I have looked at those thin plastic imitation tin ceiling tiles that they sell for kitchen backsplashes. Seems like they might work but they are horribly expensive. I could glue up some paneling, as they had done to the walls, but I am concerned the adhesive bond, even using the glue intended for styrofoam, would not be sufficient and it would fall down or sag.

Help! Any other constructive suggestions to cover this ceiling without lowering it too much or having to drill a ton of holes for fasteners in the concrete? The lighting is all wall mounted in there and the concrete is fairly smooth, dry and competent. it is just ugly (and covered with ugly foam).