I used the Universal X Sock Loom in the 1/4” gauge loom. If Cindwood puts out a hat loom in that gauge you can make a size D and up cup size.
This is not an approved Knitted Knockers pattern but can be donated to your local hospital or can be made for a friend on family.
This version is done in the round which should be easier to make than the flat version.
It has a full video tutorial and is an intermediate pattern with increases and decreases in the middle of the garment.
I used Lions Brand Coboo but you could probably make 2 breasts with one cake.