There are a number of manufacturers who make rack-mounted Static Transfer Switches (STS’s) for exactly this purpose. I suggest you do a web search, or contact your UPS and PDU supplier for recommendations.
The two cords of an STS are connected to your Redundant PDU’s, just like any other dual corded device, then your single-corded device plugs into it. If one power source fails, the STS swings the load to the other PDU source virtually instantaneously. (usually within a few power cycles, which is fast enough for the equipment power supply to maintain operation). Obviously, this does nothing for a power supply failure in the hardware.
True “dual-corded” devices have two full capacity power supplies. Single-corded devices do not.
It is critically important to verify your circuit loading so that the transfer of loads to either PDU doesn’t overload either it or the UPS, which would cause a major shutdown. This solution works equally well for the “odd” power supply in 3-corded devices that require two of the three supplies to be powered for operation.