Making your own supports in situ is perfectly possible, and they will be tailored to the individual requirements of your roses or clematis or clump of asters. You don't need a team of gardeners; just an ax, a mallet, and the ability to form a circle.
Using different plant material for twisting can lead to some wonderful color combinations, though it will fade after about six weeks.
With the ends of the rods which you may have cut off in making your circles, or with thinner material (for instance weeping willow) bind the joints tightly, tucking in the ends. If you want to create a mesh in the middle for herbaceous plants to grow through, sharpen some more rods and push them into the hoops and across to the other side. It will be stronger if you weave over and under as you go (see above).
It is more practical if a wigwam does not come to a peak at the top, for the sake of the flowers,
Making a Willow Wigwam is Easier Than it Looks : amazon