Patterns for children's ghost costumes are available online and from Halloween stores. A person can order these patterns and create their own ghost costumes for their children.
Depending on the age of the child, you may be looking for a cute ghost costume or a scary ghost costume. Here are a couple of websites which offer a wide variety of both, and are reasonably priced: http://www.bizrate.com/kids-costumes/kids-ghost-costume/ http://www.sortprice.com/search-CQ-Children's_Costumes-Ghost If you prefer to shop in person, local department stores also offer a huge selection. You might want to visit any of the following: Walmart K Mart Target
superhero pumpkin ghost princess clown fairy
You can find a kids' Jane Banks costume at costume stores, online retailers like Amazon or HalloweenCostumes.com, or at stores specializing in children's costumes. You may also be able to find DIY options or sewing patterns to make your own costume.
party city
usually you find them at stores during holloween or you can go online and find one
You can find some Halloween ghost crafts for kids at http://www.dltk-holidays.com/halloween/ghost_crafts.html. You can also find ghost projects at http://familycrafts.about.com/od/ghostcrafts/Ghost_Crafts.htm
I don't think there is a kids Halo Spartan costume out yet.
You can find a monkey costume at http://www.buycostumes.com/browse/Animals-Insects/Kids-Costumes/_/N-mZ3l/results1.aspx or else at your local mall. Hope it helps.
Pottery Barn Kids Fairy Princess Tutu Costume is adorable.
Police officer costumes for adults and kids are very popular and it makes them easier to find. Check out these websites for a variety: http://www.buy-cheaphalloweencostumes.com/police-costume-for-kids/ and http://policemancostumes.com/kids-policeman-costumes.php.
No one specifically makes them for kids but if you look at amazon or ebay or ext. you could find some that are tailored
The best place to find video for window washers that dress in costume for sick kids hospitals would be on Youtube. Youtube carries an assortment of videos to entertain the whole family.