I bought one of the round convertible type reflectors. Without the covering it is a diffuser. Slip on the cover and one side is a white reflector and the other is gold. Reverse the cover and the reflectors are silver on one side and half gold and half silver on the other in a tight checkerboard pattern. Very handy. Unfolded, it measures approximately 1M in diameter. In hindsight, I should have bought something bigger like
this. With light sources like reflectors, softboxes, and umbrellas, bigger is almost always better if you have enough light to throw at them. The bigger the light source, the softer the light. Small light sources are ok for things the size of a head and shoulders portrait and smaller. If you want to light a whole figure, you need something big and close in. It's easier to subtract light from a large source than it is to get a small source to cover something big.
I have made reflectors up from white foamcore. It's very inexpensive to do this and it works quite well. The problem is bulk. It's not heavy, but it doesn't fold up into a small package and it is fragile. Works fine indoors in a studio setup. Damned inconvenient if you're transporting it across town without a car.