Where could I find knee high black leather boots for my wife for Christmas?

I am looking for something sexy but not slutty, any ideas? Any certain style or heel hight that might be good?

Try these my man
http://www.zappos.com/n/p/dp/21542204/c/3.html
or
http://www.zappos.com/n/p/dp/21267429/c/14004.html
or try the nine west link at Zappos.com
http://www.zappos.com/n/es/d/722443800/heel_height/4/show_all/1/page/2.html