K here is some info about cruising rivers in the USA including the Columbia and Snake rivers.  The boats available I think are nice. 

 

American Steam Boat Company:  Mississippi River, Ohio and Tennessee Rivers, Columbia and Snake Rivers.

 

Unicruise Adventures:  Several places around the world including the Columbia and Snake Rivers.

 

American Cruise Lines:  All over America including the Columbia and Snake Rivers

 

Lindblad Expeditions/National Geographic:  All over the world including Columbia and Snake Rivers. 

 

Thanks to WeCruiseToo for the additional info.