I can not find the photograph now but a member here made one out of two buckets and some pvc pipe. He cut the bottom few inches off two buckets and somehow attached pvc pipe to the center of them. He then fabricated what can best be described as large "hairpin" out of pvc pipe with a couple of 90 degree elbows. He installed it from the dock under the pulpit and tension from the hairpin kept the buckets in place.
I'll try finding the picture later. I promise it was an ingenious idea and far simpler than I described it.
That was me and it is still working well. I can't search for my post as the Android tablet app doesn't appear to have a search function. The desktop version does, and I will post later if somebody else doesn't beat me to it.
The ice-cream containers lasted about a year due to sunlight/UV degradation. I have since used the old containers as molds to make fiberglass versions. Very easy if you have some minimal experience in fiberglass work. Well worth the effort if your boat spends as much time as mine does parked in a high-fouling environment.