Well I was also looking for a specific 8600 waterblock but couldn't find any. Meanwhile I just used the zalman waterblock that I had on my 7800 and there is no problem... same fixation patern etc...
So I decided to buy the DD Maze5 to make my new build and hopefully it will fit the same way.
So unless you are looking for a full cover waterblock I suppose any nvidia compatible GPU waterblock should do.
I will let you know about the DD Maze5 as soon as I got it, should be ina couple of days!