Eastwood makes these:
http://www.sears.com/shc/s/p_10153_12605_SPM6316778904P?sid=IDx20110310x00001i&srccode=cii_184425893&cpncode=35-14670418-2
They've been around for years. I have a set. They work great for low-torque applications. They get inserted into the next larger size wrench than...