Have you been able to fix it? Hate to buy new boots, as Danners aren't free.I have a pair of danners that do the same thing. I think that it is the pull tab on the back of mine is where the noise is coming from.
It could be the insole. Remove the insole, sprinkle some baby powder in them and put the insole back in. It could also be the laces. Try putting some boot waterproofing wax on the laces. Or it could be the leather itself if the boots are dry and/or dirty. Try cleaning them around the stitching and put some waterproofing wax on the leather, especially around the stitching. The wax in the waterproof could help stop the squeak.