I surely am! :) I plan to do Luna Lovegood or just a regular Ravenclaw student for Halloween. Here are some links:

http://mountland.livejournal.com/53265.html#cutid1
http://diyfashion.about.com/od/costumes/ss/gryffindor_robe.htm
http://www.dartheagle.com/hp_tutorial.html

A few are house specific but I’m sure you can put any colour that you want for the lining. And if you’re in need of a patch, I’m pretty sure there are many places to find them but they are available on amazon.com.

Why pay $100+ for a robe when you can make one for so much less?