Why would you want a wooden tunnel? The fun of the tubes is seeing them run through the tubes. I'm sure they don't want to do this in the dark, it wouldn't be fun for you or them. I'm sure there is someone marketing wooden tunnels.
Yes. Although plastic tunnels are much more common and easier to find, a google search will reveal a number of sites that sell small wooden tunnels. Of course, I still prefer the toilet roll tunnels personally *smile*.