Well, there's the PH Cutters that Saini06 suggested, like Cyanostane (which is my personal favorite product of all time), but I'm not sure what kind of bulk stack you just came off of, something natural or something Pro Hormone. I'm guessing something natural. Stims are anything stimulant based, usually a combination of caffeine and 1,3d these days. Non-stims, are weight loss products that don't stimulate your central nervous system at all, but burn fat through a different pathway, like stimulating your thyroid, such as Shift
Synthetic Supplements Shift or something similar but with a mild stim, like Alpha T2
Orbit Nutrition - Buy PES Alpha-T2 Extremely Cheap!. DCP is also popular
Orbit Nutrition - Buy Genomyx DCP For A Discounted Price, that help assist in fat oxidation by pushing fat into your mitochondria, basically.
If I were trying to put a fat loss stack together, I'd go with some form of a Stim Based product, like Decimate or Oxy ECA as Packers suggested and add some non-stims alongside it, like DCP or Shift (or just run a stim based product solo; stim based weight loss products tend to be superior to non-stims).