Where can I buy/find an American Indian costume for a little girl in San Diego, California?

Well, Brings Light is correct, a costume doesn't make the person and "costume" may be a poor choice of words, but, you didn't say why you want the clothing for your little girl so I won't assume it's for the intent of, even unintentionally, degrading or stereotyping any group of people.

So hoping this is an opportunity for education, instilling cultural sensitivity and learning that the American Indians are a large and diverse group of people with a great history not only in San Diego County but across the country and they are a people with a vast, rich culture and are more than just casino operators I'll include the info below. And hopefully she'll have some fun too.

Sometimes dressing up is a great opportunity for kids to have fun and learn about other cultures and people. My kids used to have regular times in school where they would dress in clothing native to a region or peoples and do a report. They learned a lot and had a good time doing it. I really don't think the people of Germany were offended because my boy wore lederhosen to school and wrote report on life in Germany in the 18th century, at least I hope they weren't.

Try here:
Buffalo Breath Costumes Company
2050 Hancock St.
San Diego, CA 92110
(619) 297-1175

It's just west of the I-5 freeway near MCRD.

Pechanga?

The same place you'd go to find a Black costume or Jewish costume...NOWHERE!

It is in extremely bad taste to dress your children as a person of any ethnic group. (You wouldn't dress your little girl up in black face or in clothing emblazoned with a yellow star would you?) Clothing do not make a person American Indian, Black, Jewish, etc. One is born that way and has no clothing on when that occurs. I am an American Indian because I was born that way. My parents are American Indian as are my grandparents. Whether I have on a bathing suit or a Burger King uniform, I am ALWAYS an American Indian.

Brings Light is 100% correct, so I can't add anything to be better than her answer. And besides that we don't wear costumes!!