Previous Season Exotics - How?

Apologies.

I've come back to Div 2 after about 5 years. Still love the game like I used to, really enjoying the added content over year 1.

That said - I feel I've got a pretty solid understanding of the game after playing two months or so.

But the thing that's eluding me is some exotics. Specifically previous season rewards.

I can't seem to find any stable information on how to get certain armor / weapons.

Pakhan, Tinkerer, Tempest, Birdie bag.

Is there a website out there that gives more detailed information on how to acquire these exotics?

From what I understand some are tied to missions?

Thanks!