If you can’t find one here, try Fish307.com. There are two different pulleys in that style. One is for a standard boom ($30) and the other is for the telescopic boom ($16).
Looking for either a single starboard seat or a back to back seat (similar to pic below). These are the wider seats found on a Baha 285, 299 & 313. Must have the fiberglass base. Send me a PM with a pic if you have one or know someone that might be willing to part with one. Thanks!