solar panel steam relief valve

I need to replace a faulty steam relief valve on my solar hot water collector. It is a threaded valve best I can tell (TACO 400-2 145 psi 240 F). I cant seem to find where to get one that is a replacement for this. Since it threads into the copper piping on the outside of my collector I really dont want to mess with having to modify the pipes to fit a differnt kind of valve. Any idea where I can locate a compatable replacement?

Thanks

Air Purge Valve - Solar

Here is a purge valve I am using on my thermal system. The automatic purge valve cost around $15 and has: half inch pipe thread.



I bought mine at DudaDiesel