You can buy some great items from Cathy at T. Bumpkins & Co.
Washable and reusable dog and puppy pee pads, belly bands, and diapers at T. Bumpkins & Co. and you can get some great boots, sandals, tennis shoes, etc. from Karen at AllDogBoots
Dog Boots | Dog Shoes & Dog Booties. Both ladies are wonderful to deal with and have very high quality items. There is also a thread that lists all the vendors on this site. I buy some boy things from Petco. Petsmart usually carries boy clothes.