Amazon has Performance Tool 3/8″ Drive Ratcheting Breaker Bar Adapter (W38137) on sale for $11.69. Shipping is free w/ Prime or on $35+ orders.

Features:

• Converts any breaker bar or sliding T-handle into a ratchet
• Hex bolster for use with an open end or adjustable wrench
• Works independently as a thumbwheel ratchet
• Made from heavy duty chrome vanadium