Problem With The Item Black Tunic

Based on wynndata.tk, you can get all Black Set items from Shadow Spears Bandits.

I've been killing them for 1-2 hours now. I got 2-5 pieces of each slot... EXCEPT FOR THE CHEST ARMOR SLOT!
However, the one Chestplate they drop is the Adventurer's Tunic.

Is this a bug / an oversight on their drop table or am I just incredibly unlucky?
Other than killing these bandits and the ones in the other side of the desert, is there any other way to get the Black Tunic?
The price on the market right now is 16 Liquid Emeralds so that's not an option ;_;

 

There's another way to get the Black Tunic, you can kill Emerald Knives Bandits, the coords are written here https://www.wynndata.tk/i/black+tunic