Q:

Where do I get more mannequins?

I got a mannequin in the latest for putting clothes on it and such. Can you get another one? If so how? I tried to check if you can get another one by asking Sable but I got nothing.

A:

There are 4 mannequins that you can get in the game and the requirements are as follows:

Purchase 51 items of clothing at Able Sisters and Mabel will give this to you
Befriend Sable and she'll give you this after talking to her frequently
Purchase at least one item on 31 different days from Labelle
Receive from Gracie 

Note that if you accidentally sell one of these, you can never get it back! Each character gets 4, so you'd presumably be able to start another resident to unlock another should you accidentally sell one. 
However, you cannot trade mannequins between players in any way, so if you were indeed to accidentally delete one, you'd only have access to the mannequin on your other resident. Mannequins cannot be dropped and when attempting to attach one to a letter, I could not, as you can see below:

