If you search my profile you'll see that I made a posting on 12/10/13 titled Cowl Block Plate (winter flying), just like you I was having difficulty finding a reasonably priced pair of used plates so I ended up fabricating my own which you will see in the accompanying photographs. Another good resource for information is from Cessna titled Winterization Kit number AK150-93H dated March 17, 1980 this gives more detail of the entire kit that's a little better than the IPC (illustrated parts catalog). There are three other major components that make up the kit if your aircraft did not come from the factory with it installed which consist of the Y pipe, carburetor heat box cap and the T assembly on the firewall. Hope this is helpful to you if you need any additional information or have questions just let me know and maybe we can get together on the telephone.
Note: Since I originally made this post I was successful in finding a very good used set of baffles, they are hard to come by used.
