There are a few folks that make dories for use on the Colorado. Some are using a foam core or honeycomb material. These materials are encapsulated in fiberglass and epoxy, most commonly in a stitch and glue format. Decking is of the same materials but occasionaly plywood. There are also plywood decked dories being built too. It is a very small marketplace, not many built per year. It takes a fair amount of time money and labor to build a quality boat. New decked dories can cost $12,000 to $15,000. That does take into account oars, trailer, coolers, etc.
A few individuals also build their own decked dories and some replicate the boats that first floated down the Grand canyon. an even smaller segment of boaters. More people build their own boats from plywood with frames or stitch and glue.
Check out woodenboatpeople.com and montana-riverboats.com to follow who is doing what. It isn't easy to find specific information unless you are savvy at using the search functions on each site.
Brad Dimock is a master builder that works on wooden river boats, both replicas and Grand Canyon River capable dories. fretwaterlines
is the link to his blog. He just finished a nice dory.
There is a seemingly nice decked dory for sale now on woodenboatpeople.com too.