The short answer is . There is no "official" publisher-distributed solution manual available to the general public or students. This is a common practice for high-level physics texts to encourage students to work through the derivations themselves. Best Resources for Shankar Solutions
If you’ve spent any time diving into the deep end of undergraduate or graduate physics, you’ve likely encountered Ramamurti Shankar’s Principles of Quantum Mechanics principles of quantum mechanics r shankar solution manual