The boat we took to Europe (62 feet LOA) and the cal 46, we had a 24" diameter "ball"--one was an inflatable plastic ball, with attatchments at top and bottom and the other was two 24" plywood circles, which fit together at 90 degrees to form the appears of a "ball". We also had the appropiate cone shape for "motor sailing" aboard both vessels.
As for smaller boats, it is not practical, and rarely excercised to use the round shape for anchoring. On the other hand, where there is not a mooring field, or the boat is not tied to the bank, an anchor light is certainly an excellent precuation.
We always used a 360 degree mast head light on our sail boats--but with the mast head from 57 to 65 feet off the water, we usually left some other deck light on. With the 62 footer, there was a long bow sprit, so we put a light on the end of it, and a second deck light on the aft or mizzen boom. This defined the length of the boat.
For the C Dory we always use a LED light at a minum--there are some bright ones which have a built in solar panel. They may not be fully legal (visiable for 2 miles), but even when the boat is stern to the beach or in a mooring field it is nice to have a light to define where your boat is. If outside of a mooring field, the the 360 degree anchor light is deployed. On the Tom Cat we have replaced the bulb with a series of LED lights, which are brighter than the single original bulb.