While the file you are looking for (the en-us ESD for SP1, x64) might be archived somewhere, installing it today creates a significant security risk.
Since Windows Server 2008 R2 reached end of support in January 2020 (extended security updates available only through specific programs), this image should be used in isolated or legacy environments unless protected by paid ESU agreements. windows server 2008 r2 sp1 x64 esd enus jan 20 full