B&H has two Really Right Stuff BH-55 Ball Heads with Full-Size Lever-Release Clamps available for purchase in their Used Department. The RRS BH-55 is a favorite of many photographers, and "Right"ly so.
The RRS BH-55 with Full Size Lever Release Clamp sells new for $489.00.
Really Right Stuff BH-55 Ball Head w/ Full-Size Clamp (Condition: 10) - $399.95
Really Right Stuff BH-55 Ball Head w/ Full-Size Clamp (Condition: +8) - $349.95