Google silospen drop calc
Click on first link
In the Search section, change the type to Monster
In the Search section, change the quality to Unique
In the Filter section, change the difficulty to Nightmare or Normal
In the Filter section, change the monster type to whatever you want (Boss for example)
In the Search section, change the monster name to the monster you want the drop information
In the Basics section, change the version to 1.13 (same drops as 1.14)
In the Basics section, change the players, party and MF to reflect what you will do
Click Find
You will get the list of every unique item (or whatever you selected), with the probability to drop that the specific monster you chose can drop. You can also get the list the other way around, for a specific item, and you will get the list of who can drop.