Cosplaytrader.com is a good start! Alright you can make a costume or go to the good will and find a nice costume or you can find some clothes that would go with you costume a kid i know did that and went as a pirate!
You could make your own Halloween costume if you are creative. The following website offers cheap Halloween costumes: www.zoogstercostumes.com/landing/cheap.php
the store probably
If you are looking for more information on what are some suggestions for cheap Halloween costumes for my son, the best place to look is on freefrombroke.com/before-you-buy-that-halloween-costume
You can find cheap halloween costumes for infants at ebay.com. You can also get one for free, just pay the cost of shipping, at thredup.com.
Go to Costumeoutlet.com.
As long as it is not past Halloween, it isn't too late to get a costume. Costume stores are open on Halloween and days before.
You can find a ninja costume for cheap at places like Spirit Halloween or at other Halloween stores. If you'd like to buy online, check on amazin or other halloween online stores.
Umpire is a Halloween costume. It begins with the letter u.
Get a costume from any Halloween store, especially from Walmart as they are very cheap and you can print coupons online. Or you can go and get a white jacket and white hat and there you are, a nurse.
You can find cheap Halloween childrens costumes by going to Spirit Halloween or going online to amazon or other Halloween costume sites online. Spirit Halloween is what I'd reccomend because it's cheap,good quality, and they have costumes for kids like bees, princesses, pirates, etc.
Target has some cute ones if you look on line but I'm not sure there's that much in the store. I think though that the best way to get a cheap costume is to wait until the day before Halloween That way there all on sale. The only drawback is that they might be out of the costume you want.
I believe the best place to get a halloween costume is from Party City.