Here you go:
https://www.tractorsupply.com/tsc/product/victor-rat-zapper-ultra-rodent-trap?store=1693&cid=Shopping-Google-Local_Feed&utm_medium=Google&utm_source=Shopping&utm_campaign=&utm_content=Local_Feed&gclid=EAIaIQobChMIvo2R9MHr_AIViBJMCh2XJgMFEAQYAiABEgIRRvD_BwE
Hang ammonia soaked rags from a 5 gallon bucket on the chicken wire just above ground level going around the pen after dark. Wear disposable gloves and mask. Do this for 3 nights. Bye bye rat(s).
Avoid putting the soaked rags near coop vents, simply space the soaked rags out about 6-7ft.