Balls Kegel

What is a good kegel exercise device for women?
I want to get one for my g/f. I’m aware of Ben Wa balls, but I also know there are other devices. Can somebody recommend a good one(s) and where to get them please???
You can do them without any device….
But…I googled it and found this:
http://www.kegeltoner.com/
Jade Ben Wa Balls and Jade Eggs for Kegel Exercise