If not, they can be made from shelf brackets, the smallest, cheapest ones you can find in your DIY store. If you use a square section boom, it s easy to fix the brackets. I use tubular booms and fix the brackets, with just a nut and bolt through the tail hole on each opposite pair of brackets. A self-tapping screw could be used for the front fixing, but I use a few turns of electrical tape secured with a couple turns of garden wire, the ends being tightly twisted together. You may want to use some hose clips for additional security.
Flexible wire is by far the easiest to handle.
I use the lightest stranded copper I can get hold of. To attach the elements, again I use tape and wire. To join the loops, I just overlap the ends and twist them together. This works fine and allows adjustments to be made with ease. Soldered joints can go brittle and snap or develop high resistance although looking OK, but if you feel happier with them, go ahead when you have made your final adjustments.