You can legally purchase ephedrine as a nasal decongestant. It is usually sold under the brand name bronkaid.
The ephedrine caffeine + aspirin stack is very effective but you don't want to abuse it. Both ephedrine and caffeine are extremely strong stimulants which will raise cortisol levels and can lead to adrenal fatigue. Adrenal fatigue is very real and something a lot of Bodybuilders struggle with. Our training is stressful enough on our bodies, not to mention our go go go lifestyles and constant stress.
i personally recommend stimulant free alternatives for fat loss like cardarine and a good nutrient partioner like n2slin from n2bm.com. You get all the benefits with no crash, no cortisol increase and no stress on the adrenal glands.