A.,
Wow...I considered this a personal challenge just to see what I could find on the net for you! LOL! I struck out in Italy. Sorry. Mexico was much easier.
Here are some websites for you to get some visuals:
http://www.mymercadomexicanimports.com/index.cfm/fa/subca...
This one shows a beautiful, embroidered, white dress that is traditional for the celebration of a Mexican Fiesta, church Kernez or December 12 - the Day of Our Lady of Guadalupe.
Here's a cheater thought for you....could you put the doll in a sleigh with a Santa? Kinda like a Dora's Christmas video?
I found this site informative (with pictures!):
http://www.facts-about-mexico.com/mexican-clothing.html
I liked this picture, too! Very holiday-ish looking:
http://www.bronners.com/1124706.html If you cannot see this pic, I went to http://www.shopzilla.com/mexican-holiday-clothing/search and I clicked on the Mexican Girl Glass Ornament.
Best of luck!
L.