The US has a lot of dollar coins in storage. Moslty at Federal Reserve Banks and Leased Space. Change the payment section of the contracts to allow payment in Coins. This would require either an address where the coins will be delivered or and andress where the coins can be picked up by the contrator.
By using these coins, which have been minted allready, the government would not have to borrow that money,
A payment of say $35,000 out of an invoice for nearly a million or multiple millions, is a small part of the entire amount, and should not be too much troble for the contractor.