Sport peppers are a key ingredient in the Chicago-style hot dog.
From Tomato Growers Supply Company's page about Sport peppers:
Sport: This Capsicum annum type of pepper is popular for its use as a pickled pepper to go on hot dogs and other sandwiches. It is especially well known as an essential condiment in a Chicago-style hot dog. Peppers resemble Tabasco peppers, but the Sport pepper is larger, about 1-1/2 inches long and 1/2 inch wide. They are medium-hot and produced in great abundance on sturdy plants. 75 days.
These are not readily available outside the US (at least in my region). What is a good substitute, particularly for making the hot dog?