Right now in Mexico you will be able to find markets filled with all of the items one needs to celebrate la Navidad in Mexico. Starting in a couple weeks (December 12) with the Virgin of Guadelupe's birthday, then to Dec 16 for the start of the posadas all the way to January 6, Three Kings Day, there are special foods, special activities and special decorations.
The idea is that after the posada (people dressed as the holy family and their entourage go from door to door looking for a place to stay the night) and when they arrive at the last house, there is a big party and the pinata game is played by the kids (and sometimes the adults). Pinatas are filled with candy and games and a big stick is used to whack at the paper mache pinata.
I've been looking for a good Youtube video about the making of pinatas but haven't found one yet--if you do, let me know!
Unfortunately, the pinatas that are available around Minneapolis are imported from China and have SpongeBob and My Little Pony plates on them.
Christmas pinatas are handmade and colorful and quite large. I don't have any at the shop but above are some mini versions that I redecorated with flowers and shiny tassels. I took one of those and ripped off the tacky decorations and covered it with flowers and ribbons (see below)--you can do that too!