I was sent on a mission by a member of the Child Development team from CPRI.  She wanted me to find her a monkey for her office.  Here you go Leslie, I have found the perfect little guy for you.  He is a Marmoset and will only be 18 cm long and weigh about 400 grams when full grown.  I warn you though, he loves to climb and can run fast.  Run it by Amy and see what she thinks.