Consider the ways in which you will use the rubber chicken. This will help you to work out your preferred size, shape and cost of rubber chicken, giving you clear parameters for your search.
Compile a list of joke shops and prop stores in your area, listing their contact information and addresses. Contact each business on the list to find out whether they stock rubber chickens. If a store stocks rubber chickens, find out the size of the chicken, the material used and the price charged. If a store does not stock rubber chickens, ask if they know of any nearby stores that do.
Repeat Step 2, contacting pet supply stores in your area. Upon finding a store that stocks a suitable rubber chicken, ask the store to hold one of the chickens aside, then go to the store to get the chicken. If no stores in your area stock rubber chickens, use an Internet search engine to find an online shop that stocks rubber chickens and will deliver to your area.