Doe anyone know if Clifford Northfield still manufactures .500 x 2.75 inch 6 micron and 25 micron diamond whetstones if so how do I get in touch with him?
I don't know about Clifford Northfield but Arceurotrade (advert on left) stock quite a range of diamond wetstones and files. You could also try Axminster Tools.
Google shows plenty of hits for Clifford Northfield so I assume they are still going? If it aint on Google it doesn't exist! [usual disclaimer, I just use it and add to the billionaires wealth]
You need http://www.buybrandtools.com. On this site you will find the full range of DMT Diamond Products both hard and flexi mounted, 9 micron appears to be the finest currently available.