where can i buy a flame sensor 3094-102 for a potterton neataheat 16/22?

where can i buy a flame sensor 3094-102 for a potterton neataheat 16/22? the probe at the end of the wire has come adrift so there for it is not telling the gas valve to allow gas to goto the burners,on the label on the orginal it reads

WHITE-RODGERS
TYPE 3094-102
USE WITH 36C80
AUTOMATIC PILOT

i am having a very hard time trying to locate this part and hope you can help many thanks danny.