I sent an inquiry to the U S Library of Congress (LOC), and received a reply. They thought that purchase orders 'may' not exist anymore. If they do exist, they said to contact the National Archives. There are sources for some information on government contracts, but they are in the process of digitizing them so they are not available for use now.

Here are a couple links that the LOC sent ...

"https://guides.loc.gov/federal-government-contracting/historical-contracts"

The LOC mentioned that if we want to research the company itself there is a guide that can help:

"https://guides.loc.gov/historical-company-research"