For portraiture we use the ones from Calumet. They're approximately 4'x8' when assembled, and 6" x 48" when collapsed. We have black, gold, silver and both opaque and translucent white panels for each. The frames are constructed from PVC pipe roughly 1" in diameter and the hardware is very good. We've never had one break, even in pretty stiff winds and rough field treatment. I'm not sure how much smaller they're made, but service- and quality-wise, that's worth checking if they suit your needs.
But you mentioned closeups. How big an area are you trying to cover?
We have a bunch of Lightdiscs in sizes ranging from 12 inches to 4 feet or so. The small ones live in our camera bags for closeups. They come in the same range of materials as the frames I described above, but are considerably cheaper and more field-friendly for smaller subjects. I frequently build a "tent" with up to four of them and clothes pins with one on each side and the back, then another over the top (all translucent white) to kill harsh highlights and fill shadows, then use another (usually a 12") to reflect light in on the subject if I want. I may only use one, two, or three as circumstances dictate. Best of all, they collapse to 1/3 the diamter when stowed.
Worst case scenario when I was on the road without light discs, I've pulled coat hangers out to square shape, then pulled a white plastic grocery sack over them. Makes a dandy translucent shadow beater as well as a soft reflector.
