I have tried little lizards and plastic goldfish. They seem soft enough, but
I sent one to my granddaughter, and my daughter said that when the little
feet, or fin, or tail starts to become exposed, it is quite a hard, scratchy thing
in the soap.
So, I found soft, stretchy lizards and frogs at Michaels. They come about a
dozen for about $2.00. I noticed that they shrink a little after the soap ages a
couple of months. I'm thinking that the plastic toy expands a little from the
heat of the M & P and later, retracts. It leaves a perfect impression of the
original shape- doesn't shrink much. I called them "ice age reptiles" because
they looked like they were encased inside of a glacier!
I have also used rubber erasers that I have found at the dollar store- 8 or 10
in a package. I think the shaped rubber bands will work well.
Have fun!