stan2004 provides good advice. Jameco Electronics is one place that has matching PCB & enclosure sets, but they are more expensive than stan2004's suggestions. I have also used these Nylon PCB Stand Offs for the inexpensive PCB's from ebay or elsewhere.
Hosfelt Electronics is another place with PCB's and matching enclosures, but they seem to be under going some changes with their website. Doesn't look like they are taking web orders anymore? I have ordered from them in the past, but not for the last 2-3 years, so not sure what's going on there?