Please note that I Do NOT want to sell mine, but I have a 1000s. I got it at an antique shop in Portland. However, i've never seen one on Ebay, or at a guitar store etc. I think they're fairly rare.
That being said, they (sunns in general) are much more plentiful on the west coast than the east (I live in Massachussets now). Old Town/Denny's music in Portland often has different sunn heads in stock, but i don't know if they have a web address etc.
Hope this helps
Shawn J