Try repeated degreasing (spray, like Brake Clean would be good), then blow dry and heat lightly with a propane torch (or even on the kitchen stove) to cook out any residue. Build up a tape, or such, 'dam' around the sight and sqeeze in some HD Locktite. Let it sit for days, then sop up whats left with tissue and let it sit a few more days. It may draw the Locktite in and set up to hold it.
You can always get more 'aggressive' later.