I have been researching cortisol suppressors for 4 months now on the net. As of now there is no substance that has a clear consensus of support. I take pregnenolone (combined with dim to prevent gyno), beta sitasterol and phosphatadyl serine for myself.
There is support in the labs for magnolia extract (a lot of fakes out there though), 7-keto (suppresses test as well as estrogen), nettle root (hard to absorb), beta sitasterol (only mildly suppresses cortisol), phosphatadyl serine (must be carefully monitored as overdoses can make you a goof, it is a nootropic), pregnenolone (can convert to progesterone), progesterone (it is progesterone), formestane (it is mildly androgenic) and several others which are too expensive to get much real world feedback.
Most bbs depend on massive calories divided into many meals to partially suppress cortisol. Several androgens, anabolics, and of course insulin are effective anti-cortisol agents but I assume you already know that.