I'm betting you could make a temporary "wall" out of transparent or translucent plastic, the kind that's sometimes used to glaze a greenhouse. I think it fits into metal tracks, which you could install along the walls and ceiling and even screw to the floor (or just hold in place with a thin sheet of rubber, assuming the track is anchored to a wall). You might also be able to adhere it to the floor with those removable strips from 3M.

One other thought - use shallow bookcases placed back-to-back to create a "wall". If you have them custom-built, they could even be fit to go clear to the ceiling. Or, if you have a little more space to deal with and want a look that's less busy than a bookshelf, buy those inexpensive PAX wardrobes from IKEA (they're available in two depths, two heights and two widths) and fit them with the plain Lomen doors or even the Malm sliding doors (which can also be purchased with a mirrored front). Place the wardrobes back to back, or use a single wardrobe and camouflage the otherwise unfinished backside of it with a curtain, a mirror, a lightbox or some other treatment.

hmmm. I'd say that in earthquake country a temporary wall wouldn't be too legal in the 'legal' sense, so there wouldn't be any (reputable) companies or contractors offering that kind of product. A wall made out of bookcases or wardrobes would have to be secured somehow to keep them from toppling over on you. I mean, if you care about that kinda thing.