The back door approach Frank mentios works. EBay has them, but you have to know what you are looking for. The sales brochure is what you are looking for primarily, not the parts book one. In this case I would want one a little newer. I have a 2003. That is new enough to have most of the latest part numbers. You can always go to Marine Engine.com and SS to the latest part number. They usually give you the Sierra number option also. I really like OMC/BRP carb. kits because they have all the parts included in the kit of the best quality.
BTW: With one of these books you get all of the impellers, water pump kits, tune up kits, fuel pump kits, etc. So you are not just getting one thing, but all of the parts and accessories for all of OMC engines of the day.
Dan in TN