Dumas makes two kits for paddle wheel boats.
http://www.dumasestore.com/catalog/i...hp?cPath=47_49

The Steamer[link=http://www.oregonmaritimemuseum.org/]The Steamship Portland, in Portland, Oregon USA[/link] Portland, in Portland, Oregon USA, is a paddle wheel tug that has been restored and is still running. It is currently functioning as a Maritime Museum till a permanent site can be built to host the museum and the "Portland". You can try contacting the Museum, or the [link=http://groups.msn.com/NauticalSocietyOfOregonandModelShipwrights/welcome.msnw]Nautical Society Of Oregon and Model Shipwrights[/link] for more information about the Steamer.

Also, I believe that Taubman's Plans has a couple of plan sets for paddle wheel boats.
http://www.taubmansonline.com/

And perhaps this website could be of some use.
http://modelplans.steamboats.org/paddlewheelers.html