In the 2002 K line catalog there are the following O gauge curve tracks, 0-31, K-0302; 0-42, K-0312; 0-54, K-0318; 0-63, K-319; 0-72, K-0322; 0-81, K-0320; 0-96, K-0323; 0-120, K-0324.
To find find the curves today watch the bay, call the old Kline super stores, call the large old Lionel stores, watch the club news letters, let people know you are looking for it.