How can i hook up my amp?

i have a clic truck with a clic radio that only has 1 speaker output. i want to continue to use my radio put hook up a system to it. i want to know if they make a line out convertor that takes only one speaker output. and if not then i would like to know if it is possible to just hook up on of the rcas off the line out convertor and get spliteeres off of that to creat mor rca plugs? if there is a line out convertor can u let me know where to get one.l