Replacement part

Hello there, 
I am looking for 2 ea of the Wedgeless Window Fasteners, model or part number is World Pats 1/8R - the plastic part broke off. There is also a stamp on the metal part Can 4 to which that plastic part attaches to. Do you cary replacement parts or the complete assembly ? I have 4 windows with those fasteneres with 2 ea. Right now need only 2 but would like to find a source any addidtional parts. I would appreaciate any informaiton on the replacement parts/assemblies. Thank you