At school we have Makala-S models
A nice, fun option (my daughter has this one and it pretty good) is the Kala MK-SS .
Another brand to consider is Diamond Head
If you purchase a ukulele, please make sure it is made out of wood and that it is a Soprano. Your student will also need some type of tuner, but there are many apps and websites that are a good free option.
If you have any questions, please let me know.