B&H has Avenger, Bowens, Flexfill, Hensel, Impact, Norman, Photoflex, Photogenic, Westcott holder arms for reflectors ranging from $49 to $109. There are a lot of options.
I use the Photoflex which is one of the cheapest and I am well satisfied. It can be used in a “boom” fashion and they have a waterbag weight available if your reflector needs a counter balance. They all might have the same ability but I am only familiar with Photoflex. It will hold reflectors from 12” to 50” in width. As far as the stand, if you are planning on using outdoors in a breeze you will probably need to add weights to the bottom of the stand as you would for an umbrella or softbox.
Link:
http://www.bhphotovideo.com/c/produc...sc_Holder.html