If its one thing you can count on seeing in auctions is milk cans, milk cans and more milk cans. Seems they, along with old fire extinguishers used for spraying, that and railroad lamps, are forever on the auction block. They are pricey too, usually garner lots of bidders which drives up the price. Speaking of that, once saw an old toy truck , looked like it had been played with by a child who thought nothing of throwing it against a brick wall.....went for $400.00. I once bid on a cruet of cranberry glass....I liked it with the silver top....but not knowing much about what is good cranberry and what is phony, I stopped -- it went for $420.00 and later a fellow clued me in on what makes for good cranberry and he thought I stopped at the right time.

I don't think I've ever seen a wall-mounted one that didn't have to be manually coiled. The metal ones from the big box stores work just fine; to make them inconspicuous, you might spray paint them to blend with the color of your house.

Having done some further research since posting, I've found what I likely need is intensive roof soil. Not only is this lighter, but also suppliers can provide the unsaturated and saturated weight. For example: http://www.rooflitesoil.com/uploads/documentation/Technical%20Documents/SPECIFICATIONS/PDF%20Versions/rooflite-extensive-mcl.pdf They give a saturated weight of 1.15 g/cm3. Which equates to 1150 kg/m3. So given a fill height of 600mm, I get: Imposed load of saturated soil in planter: 1150kg * 0.6 = 690 kg/m2 or ~ 6.9 KN/m2. The roof suppliers assumption of 7.5 KN/m2 would give about 10% overhead. I imagine even if I find a structural engineer to do the calcs, they will want to know the soil used. So I guess my next port of call is to call a few suppliers of roof soils and confirm the specifications. Perhaps they can also confirm the drainage design required.

There are now some decent looking looking plastic whiskey barrel planters that are lighter than the traditional ones. They still get heavy when filled with soil. We fill part of the planters with empty plastic containers of various types/sizes (quart plastic milk bottle, etc.) before adding soil so they are lighter. The trick is to make sure you have enough soil to grow what you want to plant, places between the containers with some soil and to remember you need to water more often than barrels without the plastic filler. We have also moved them using a hand truck. It is a little tricky to get them up and balanced and three people helps to keep them that way.