Clothing and shoes can be difficult to find in terms of size as well as appropriateness of age.
Boys would seem to have a slightly easier time, since even formal wear tends to be duplicated in little boys sizes. Shoes would seem to be more difficult to find. I have recently received several inquiries regarding shoes for new walkers who don't yet fit walking shoes. While there are many things that have improved over time and many things that our children with Bloom's today will find easier than I, this may not be one of them. Apparently, it was a whole lot easier to custom order/make shoes when many independent shoe stores still existed. I apparently did well with something called a straight-lass, Thomas heel shoe. I remember having the same boring shoes year after year, but at least I had them.
As we get to adulthood, many of us will need to budget for custom made clothing, especially women in the business world--pin striped suits with below the knee length skirts are not an easy find in a five year old's size.
My advice--learn to sew! Alternatively, marry someone rich!
Ok, all jesting aside, there are several web-based companies that can assist with custom made clothing. Some of it can be found more cheaply also. Prioritize what you need to be made vs. altered, vs. what you can live with. Little People of America has some good resources available for this.