Here are some of the places I like and use to source parts and manuals for pinball and arcade restorations.
Pinball Resource – http://www.pbresource.com/
Pinball Resource owns a large stock and rights to reproduce Gottlieb parts and is a great source for many other parts as well.
Marco Specialties – Marco Specialties
Marco has a great website and parts inventory.
Big Daddy Enterprises – www.bigdaddy-enterprises.com
Great electronics parts source.
Boston Pinball Ebay Sales History – http://www.bostonpinball.biz/
Record of Pinball sales on eBay with Prices