Try ebay - I found a mint condition 2005 in late 2006 with a DHX for £350. All it needed was a new bearing. Since they were still retailing in the shops for £1200 - £1800 at the time I was pretty stoked ;D
I have some old welded up frames in the basement if you are really desperate. I also have some spare parts, shocks and MRP guide peices for the DHi if anyone needs them. Willing to send them to a good home for next to nothing.