Fedex has no PFEs.
UPS might not have any.
Airborne Express hired PFEs many years ago for their DC-8.
One problem at Atlas is that they have reportedly hired their PFEs and pilots (for FO and Capt seats), who all retired from the US military squadrons. This seems to be because they already get a paycheck from the US government and it was considered an extra supplement to the small paycheck they received from Atlas. For some simple, but misleading basic numbers, check the website "airlinepilotpay.com".
Kalitta seems to have PFEs for their 747. Have no idea whether the company requires experience, same for Polar. On the DC-10, Gemini might be a possibility. Good luck.