Easy fix for a saddle that might work for yours. I had a new WTB saddle, and it was very creaky. Did all the usual -- talc/oil along seams of leather, tightening bolts, etc. Nothing worked.
Then, I tried flexing/bending the plastic "form" over which the leather is stretched and attached (along the sides of the horn of the saddle). Worked like a charm. The form, being new plastic, hadn't undergone full deformation, and so the creaking was caused by the continual springing action of the plastic as it flexed and then returned to its original shape. After fatiguing the plastic by hand, I haven't heard from it since.