When you say stimulant I believe you are asking for weight loss stimulants and not just wired up junky endless energy stimulants.
Well the common stims used in body building are Caffeine, Ephedra, and Clenbuterol. A fourth one is out there, but I can't remember the name as I quickly forgot about it when I heard about how bad it screwed with your thyroid.
Now all the above have some effect on your thyroid. Caffeine is the only legal stimulant for body building.
Ephedra is available in Bronkaid, you used to be able to get this over the counter, but I heard that has changed. Ephedra is not legal to be used in weight loss supplements and I believe the company that made it famous in weight loss supplements was Hydroxicut, but they had to stop using ephedra back in the 1990's. Ephedra though gets your heart rate up and some people were developing heart issues from its use. Common weight loss stack is a Bronkaid with a childres asprin everyday and it comes close to what Hydroxicut had in its original formula.
Clenbuterol is brutal on the system. Yes, I use it. Yes I sleep with a pile of towels under me if I sleep at all! I do not recommend this for someone new to stimulants. You have to feel this one out and some people do not tolerate it at all. If gives my wife a migraine with just 10 mg. I take 80 mg and seem to just sweat like crazy. Clenbuterol is illegal and can get you in trouble with police.