his Manfrotto R354.08 Locking Lever Assembly is included with the compatible tripod heads, and is sold here as spare or replacement parts.
Photo tripod accessories
Manfrotto Part R354.08 Locking Lever Assembly for 410 and 405 Heads
Tripod heads: 329RC4, 405, 410, 468MGRC4, 468RC4, 488RC4, 498RC4, 808RC4, MH055M0RC4, and MH057M0RC4
$25.00
Tripod heads: 329RC4, 405, 410, 468MGRC4, 468RC4, 488RC4, 498RC4, 808RC4, MH055M0RC4, and MH057M0RC4