Slime omok piece

Could someone please tell me whether slimes actually drop these? I know that mushroom piece is dropped by mushmom, but I don't want to be standing around grinding on slimes all day...

Grinding on green slimes for about half an hour and found one. CONFIRMED

Just check the monster book, if it aint there, you wont get it as a drop.
In the old days slimes dropped them at a low rate, just like orange mushrooms dropped theirs.

The monster book is incorrect. For instance, omok table drops from Toy Trojans (for sure, found two today) but it isn't in the codex.
Same with the mushroom omok piece, it drops from mushmom, but it isn't in the codex.