Purple Sea Rod, Plexaura flexuosa, comes in several shades of purple. They have thick, smooth branches that become fuzzy purple/brown when the polyps are extended. Larger ones are available at a higher price, mostly because of the extra shipping cost. This particular species is a little more difficult to ship and to keep, but if it makes it through the shipping process and the first week in your system, it should do fine for a long time.
We have started to also get frags from colonies in the ocean which means it is possible that you will get a gorgonian on a frag plug. It just depends where I went diving and what was available.
Nano: 2 to 4 inches
Medium: >4 to 6 inches
Large: >6 to 8 inches