Had a bit of a think and came up with an even lower tech alternative. The advantage with this system (apart from zero cost) is that the height is easily adjustable.
The clothes pegs are simply tied to a piece of garden cane with thin nylon twine then glued for extra strength. I filed a notch in the pegs and cane to stop them from sliding sideways.
Works with one or two uprights but obviously 2 canes are more stable in very windy weather; like today.
Might have a think about some sort of really strong alternative to carry around without any fear of breakage. Possibly construct a telescopic version for easy transit. Perhaps those thicker garden stakes, like Mike suggests, might work. Otherwise it may mean considering using stainless steel rod and tube and some sort of clips. Wonder if any of those marital aids catalogues have any suitable clips!