The following spreadsheet is a list of items I purchased for the construction of the oven. A number of items were already in my scrap bin, including one kitchen oven (I'm a remodeling contractor and frequently haul old appliances to the dump). Another oven was picked up (literally) from the side of the road. The thermostat ,heating elements, and view windows came from these ovens. The steel for the trolley and rails had already been purchased, and was left over from a prior project.
The contactor was purchased from an air conditioning supply house,and in fact, is very similar to the contactor found in the condenser unit of many home A/C units. This contactor has a 50amp capacity with a 110v coil. See the links page for a supplier to purchase the contactor online.
I've received many questions recently about where to purchase the insulation board. The product is a 2" thick, 3PCF rigid, unfaced fiberglass board. It's made by several different manufacturers. I've listed the manufacturer's websites on the Links page and recommend that you visit the websites, look for their "Find a local distributor" page and contact distributors near your location. I purchased the Knauf board from a local distributor named General Insulation, and it appears that they may have warehouses around the country. A Google search would probably confirm their other locations. Beyond that, I can't offer any online sources, or other advice on where to purchase it.