For the Lord Voldermort costume we used an old mask and black cape from our costume trunk. The snake came from Dollar Tree. After the picture was taken my son decided he didn't want to go as that after all. Since he claimed he already had the hair he decided to go as Professor Snape.
The Snape costume was easy to put together using his black pants and dress shirt he wore to a school dance. For the stand up color he wore a white dress shirt under the black one. For his cape he borrowed his brother's graduation gown and I made his wand. His black shoes are his dad's from the AF. I made his wand.
At the book signing they passed out house badge pins that just added the finishing touch to the costume.
For my McGonagal costume I found the green material on the dollar rack at Wall Mart. I used one of my Renaissance patterns to make the cloak. It took about 5 yards of material and about two days to complete. I found a round broach in second hand store for about $3 and glued tan colored rhinestones on it. I owned a long black skirt and borrowed my mom's black shirt and pointy black shoes. I got a cheep black hat and bent it over and added a few feather's to it. The square glasses came from a Santa costume my mom had. Again I made the wand. The books just came off the book shelf.
The wands were real fun and easy to make. I rolled up plain paper pretty tightly and taped it closed. Then I painted them black or brown and added hot glue for the details. Once it dried I just went over it with sliver or gold paint.
My son got tired of carrying his around so he gave it some little Harry Potter at the book signing. We had a lot of fun that night and several people asked to get their picture taken with us.