Here is a site that should help you.
http://www.homeschoolblogger.com/picketfencemom/243321/
I've seen these cones sell anywhere from 4-7 dollars.

I just did these for a craft show this weekend-they did well-The homeschoolblogger wasn't very clear so this is what I do - first check the dirctions on you cocoa mix - the cone makes hot chocolate for 2 - you need two bags - fill one bag with measured cocoa close with a twist tie - slip it into bag two (make sure the seams match up - Put in a few marshmallows = spinkle with mine chips or the colored ones lokk real good too - repeat with marshs and chips- twist tie and curly ribon shut - I found a mug graph and put the following saying on it and tied it on the ribbon Good Luck!!
"Hot Cream Cone"
Hot Chocolate Mix for 2
Divide into two mugs
Add boiling water, stir.
Top with marshmallows
and chocolate if desired

For some really nice looking ones, check out the conversations side on the Painting forum. One of the members there shared pics of her craft show booth and she sells them. Don't know if she would be willing to share instructions, but couldn't hurt to ask her. Luvs