Given that it's a low tier unique, your best bet may just be magic find (MF), or anything else that drops generic uniques (heist chests, blight chests, etc.). Boost your own item rarity with items and/or item rarity support, juice the heck out of a lower tier map (make sure it meets your unique minimum level), and dump in a bunch of rare/unique monsters. You can also combo your titanic and anarchy scarabs with anarchy on the map device.
Chancing is something like 1/300 to get a T4 unique, but I think it's kinda fun. Make sure your white base shows up on your filter, carry a stack of chance orbs, and just grab->chance->drop when you run across one.
If you see your item base in Gwennen, go for it, but I don't think it's worth trying to farm expedition.
On the wiki, the minimum drop level is shown as "Drop Level" in the "Acquisition" box on the right (e.g. 77 for https://www.poewiki.net/wiki/Leper%27s_Alms). If you don't see one, then it is the required level to use. This doesn't affect Chance Orbs, but does affect Ancient Orbs.