In a high wind a reflector also doubles as a really good kite. But in a moderate wind I use a Photoflex reflector holder. I bought it when I bought my reflector. It’s basically a stand with a cross arm on it that has two clamps. But even this will blow in a wind so I add a couple of weight bags I got from Photoflex also. They fill with water and have a hook that goes around the stand. Use one for light wind and 2 or 3 for heaver winds. Since the bottom of the reflector is not clamped to the stand it will still blow back and forth even with the weight bags keeping the stand in place so get another clamp from a hardware store and attach it to the bottom of the reflector and tie some string to it with the other end to a couple of tent stakes you can get at any sporting goods shop. Or you can tie it around a couple of rocks also. I find this combination works great and doesn’t cost very much to put together.
I hope this helps or at least gives you a few ideas to run with.