The clock industry has changed over the years. Many of the better brand clocks are no longer to be found. Variety is also limited. So depending on what type style and price range you are looking for it is tough to tell you. How large?? Are you talking clock motors or inserts??? Clock inserts come in 3 catagorys, good better and best or economy, standard, and premium.
Here is a good past thread from here that may interest you.
www.scrollsawvillage.com/topic/21804-clock-inserts/?hl=%2Bclock+%2Binserts