On the Colorado near Austin try TG Canoe out of San Marcos. Near Columbus on the Colorado talk to Howell Canoea. All very good, very knowlegeable folks.
On the Neches and Trinity, I know there are a couple, but its been to long to remember names. Maybe TexasLady will see this and respond. They know some of the East Texas outfitters pretty well.
Village Creek is a nice trip also.
Kayak Motor Kit