You can use Multiwfn code to generate .47 file based on GAMESS-US output file.

First, perform GAMESS-US calculation with default "NPRINT" option, then change the suffix of the output file to .gms. After that, load the .gms file into Multiwfn, input below commands
100  // Main function 100
2  // Generate input file of quantum chemistry codes
8  // Output current wavefunction as .47 file
test.47

Now you have test.47 in current folder, which is fully compatible with all versions of NBO. Note that the .47 obtained in this way doesn't contain Fock matrix, therefore E2 analysis will be automatically skipped by NBO.

By the way, Multiwfn is also able to generate .47 file based on .molden and .fch files generated by various quantum chemistry codes in the above way.