I think you may have difficulty locating a purpose made tank,
Try Googling it with the make and model number.
Although you could start by asking the neighbours, who you say have already experienced the problem, what they did.
I would think that a water storage tank is a storage tank.
This is from internet. It explains how someone installed a storage tank to replace the original in a solar system, which like yours, rusted through. I think that is what I would do, but it depends how skilled you are though.
(sorry about the underlining, I could not get rid of it)
The conversion process
Look for a tank that has at least one extra removable 3/4" plug on the top. Don't confuse the anode rod plugs with an extra plug. The one I got has two. I only used one though. Make sure there is no check valve or restriction on the cold water intake side. If there is, remove it. Mine had a rubber flapper. I removed it with pliers. If you don't remove it, the water pump may have trouble pulling water back from the tank. Take 6' of 1/2" copper pipe, solder a copper 3/4" thread to 1/2 pipe adapter and solder the adapter so that the bottom of the pipe sticking into the tank will end up about 12" from the bottom. Screw this assembly into the tank using teflon tape on the threads. cut off the remaining 1/2" pipe sticking out - leave about 4" above the adapter. Solder a ball shutoff valve to the that. Add some small pieces of pipe and elbows. Add a anti-siphon check valve if you don't have the electric shutoff type and some more pipe to run to the hot output side of the solar panel. Add a tee to the cold water intake and adapt it down to the intake of your water pump going to the solar collector panels. The other option is to use another spare plug and do the same thing but with a 1/2" pipe that is only 6" from the bottom of the tank. This way, you don't have to remove the check valve built into the tank - if it has one. Once everything is soldered. Apply water pressure and check for leaks. Insulate all your pipes. Don't use that cheap poly stuff, it melts within a week when exposed to the high temperatures of the solar heated water. Now when the panel is hot enough, the motor will turn on and draw water from the intake side and the hot water will go through the check valve and into the water tank.
This message was last edited by johnzx on 22/03/2013.