Here’s Stewie doing his coins in a piggy bank trick. The blue piggy bank is just a ceramic bank I picked up at a toy store. The “coins” are plastic disks from a Connect Four travel set.
The coins in the piggy bank trick was taught the same way as rings on a peg (which in turn was a variation on retrieving/putting a ball in a cup). You can find parrot clicker training resources here (scroll down to the Getting Started Clicker Training for Birds book).