Windows 7 ISO

[pantau]

Try it:
the file bootmgfw.efi can be extracted from a x64 Windows 7 DVD: It is located in the 2.7 GB archive Install.wim in the subdirectory \sources. The archive can be opened with the free 7-Zip packing program, for example. The file you are looking for is then located in subdirectory "1" of the archive, under \sources\install.wim\1\Windows\Boot\EFI\.
Create the folder boot in the folder efi and copy the bootmgfw.efi into this folder. rename bootmgfw.efi to bootx64.efi.

I found the file on the same ISO, however, neither 7-zip nor WinCDEmu allows me to write to the ISO.

[Van Flusen]

Try it:
the file bootmgfw.efi can be extracted from a x64 Windows 7 DVD: It is located in the 2.7 GB archive Install.wim in the subdirectory \sources. The archive can be opened with the free 7-Zip packing program, for example. The file you are looking for is then located in subdirectory "1" of the archive, under \sources\install.wim\1\Windows\Boot\EFI\.
Create the folder boot in the folder efi and copy the bootmgfw.efi into this folder. rename bootmgfw.efi to bootx64.efi.

I found the file on the same ISO, however, neither 7-zip nor WinCDEmu allows me to write to the ISO.

Use UltraISO or something similar.