I maybe a little late for this but if you go to some Latino markets they sometimes have a powder version of Chicha Morada made by negrita, basically you make it like you would koolaid just by adding sugar. I have actually found some peruvian restraunts use this to make thier pitchers of chicha that they serve to customers. You can try to buy premade chicha from the local restraunt but I think that would probably be very expensive in the end. Even going into a market that specializes in peruvian food it's hard to find premade batches of Chicha morada. My wife makes chicha from scratch she just goes to the local latino market buys the ingredients (purple corn found in the peruvian section, pineapple, apples, cinnimon, cloves, limes and sugar) and makes large batches like 3 gallons at a time.