For pure silver cables at a somewhat reasonable price, check out Moon Audio. www.moon-audio.com. They make custom cables and you can ask for microphone cables, even though they aren't on the web page. The price for my mic cables was also significantly lower than listed on their web site. They will also throw on any type of connector that you want (straight, right angle, gold, silver, rhodium, etc.). I asked for some right-angle silver Neutrik connectors and they said that it was not a problem. The rhodium Furutech ones looked absolutely fantastic, but cost a fortune; something like $130 for a pair.
Zaolla also makes a very nice pure silver cable at a cheaper price than Moon Audio, but I found them too heavy and rigid for easy use in the field. Audio Magic also makes pure silver cables. Very nice, but they will cost you a little bit of money. Some of the other one that I checked out like Analysis Plus and Van Den Hul are either pure copper or silver-plated copper.