Gnashing Sash, Death Articulated, and Bursting Decay items

These three items seem unattainably rare due to the double restriction of being enemy-specific from a corrupted nexus unique enemy AND an ultra rare item on top of it when those enemies do not drop a guaranteed unique. There are less than 100 Gnashing Sash available on the whole trade league right now.

This is coming from an admittedly niche perspective, I am an SSF player who enjoys the fun of completing the uniques collection. In the in-game stash tab I have 365/375 unique items and I am worried I will never have any opportunity to acquire the three items mentioned in the title.

Rare is great! Rare is fun, and very welcome. But it would be nice if there were some way for an SSF player to obtain these items realistically. Right now, numerically it doesn't seem possible even in a lifetime of playing.