I see your point about accessing the Kayak Classifieds.
What you could try is going to "Kayaks" again, then up at the top where it shows those two sub-categories, click on the the link to the last post under the classifieds. From there, once that pops up, I think you can select "New Topic" and add your "ad." Why this circuitous way, I don't know!
Hey! What year model is your kayak? Any more info?
And, have you also listed it on FaceBook under the Dallas/Fort Worth Kayak group?