Demand for failsafes have been hurt by all the radios on the market since many incorporate the failsafe into the radio. Thats the reason I don't run one anymore - my 3PK has both a low batt and loss of signal failsafe.
I used to use a small OFNA failsafe like this one -
http://www3.towerhobbies.com/cgi-bin...&I=LXEYG2&P=ML
I still use a rubber oring looped around the carb and where the servo attaches to the carb as a throttle return.