Some links I found (I'm not limiting them to 100%, since some synthetics could add strength):

80% Wool Navy Blanket - $23.95:
http://www.armysurplusworld.com/product.asp?engine=froogle&productID=10122

100% Wool French Blanket - $19.95:
http://www.armysurplusworld.com/product.asp?engine=froogle&productID=10126

80% Loom Woven Blankets - scroll down toward the bottom - these are my personal preference even though not 100% - $29.95:
http://www.vtarmynavy.com/wool_blankets.htm