There are heaps of ways to introduce someone to it, but she needs to be open for it.

So talking to her would b the first step. 

Or you know her that good and just gift her one or if she likes to control you instead, get one for yourself as suprise ?

Do you ever used toys in the bedroom?

Have a few drinks. Bring it up and ask her which one she would be interested in. Ease into it. Don't be pushy. Sometimes they are shy about it.