Little Red Riding Hood costumes are one of the more easier to find costumes. Wal-Mart would be my first recommendation, you can also try spirit Halloween this is a store that opens thru out the US for a short time just for the Halloween season.
You can take a long piece of red fabric and pin it to transform it into a red hood. You may be able to find a plus size little red riding hood dress for your husband at "Costume Express".
Walmart,target,and Halloween stores.
You can find a good hippie costume at costume express. They carry a bunch of different costumes and they are just a costume store so they would be the best place to look for your hippie costume.
I would suggest http://www.wondercostumes.com, it looks like a good place to find a costume you want. I saw that it has costumes for kids and toddlers. Hope you find what you're looking for.
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!
www.BuyCostumes.com
You can use a red tee shirt and pair it with a red poodle skirt. Make sure you tie a huge red bow across the skirt. Then you should be able to find or make a red bonnet and get a small basket to complete the illusion.
Some great couples costumes for halloween might be peter and wendy from peter pan or robin hood and maid marion or even shrek and fiona another good couples costume would be little red riding hood and the wolf
You can find good adult costume for cheap at walmart, K-mart, Target and other stores. You can find them online at websites like ebay.com,amazon.com, and partycity.com
The best place to find a good Minnie Mouse costume is at the Disney Store. Disney Stores are located in major shopping malls throughout the United States. You may also get a good deal on a Minnie Mouse costume on eBay.
To find good costume wigs, I highly recommend going to a costume store. I'm unsure of your location, but many places have stores set up only for fall where they sell costume wigs. A good place on the west coast would be Costume Castle, but any stores such as Wal Mart or K Mart may have a decent selection.
You can find a mator costume in many stores. Examples would be Walmart or your local Halloween store. A good place to get prices is from Walmart for a mator costume.