A retrofit ice making and bagging apparatus and retrofit installation method provide automatic supply of bags of ice into a freezer compartment. The apparatus has an outer housing with a lower end configured for securing on top of an aisle freezer so that openings in the lower end of the housing and upper end of the freezer are aligned to provide a passageway into the freezer compartment. An ice making unit and bag making and filling station are mounted in the housing. Ice is transported from the ice making station into partially formed bags at the bag making and filling station, and a bag is sealed and separated when a sufficient amount of ice is supplied to the bag. The bag making and filling station communicates with the passageway into a storage compartment in the freezer, whereby separated bags of ice fall into the storage compartment on completion.