Black Heron in Longview, or Pritchard's Western Angler on the Kalama. My friend worked at Black Heron, and said it was a good shop. Pritchard's has a great phone-in river report, they give good info, and have a cheap shuttle. Good luck.
There is also Greased Line Fly Shop in Vancouver. I know it's a few minutes down the road, but though I would round out the options I also recommend all the above.
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