exemestane or AIFM (TD/topical ai formulation- OTC)
if you are doing aromatase inhibitor research, you can get exemestane, letrozole or anastrozole from researchstop.com.
as a note the oral AI's ATD, formestane even 6-oxo (though high estrone metabolite conversion) do "work". they just have VERY inconsistent uptake and very short half lives. They tend to cause more issues than they help with by either inducing ultra high suppression for a short period or almost none at all (highly variant plasma uptake of doses ranging from none to 3%), either way with the half life issues they cause wild swings in aromatase levels which are endocrine disrupting.