I buy mine off Amazon but you can find them in most hardware stores. They are high quality bits that keep their edge and cut very clean. I have used both the 1/4 inch and 1/8 inch endmills, ballnose mills and several different v-bits they make. All have had the same great quality and never had a problem with them.
They are middle of the road in cost but quality matches most expensive bits. If Phil recommends them they must be good with the quality of his carvings.
Just search Amazon for Whiteside router bits and you will be able to find what you are looking for. Just remember, they are router bits so you may find several that are not appropriate for the CNC unless you really know what you are doing. For example, Roman Ogee bits