The parts catalogs have breakdowns of all mechanical components and give part numbers for all the hardware. It may be a bit time-consuming but you'll find the occasional onesies and twosies in game-specific components which aren't used elsewhere that you'll be glad you ordered. Here's the catalog that includes Pinbot:
http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_Blue_16-9064-B/index.html#/1/