N.B.
Think Baby is a great brand with a silicone nipple, my daughter loves hers and it's BPA free.
They come with a removable handle, too, for when they are big enough not to need it anymore. We've never had an issue with leaks and we have three of them that are abused daily.
There are several other brands out there, especially nowadays that it's become an issue of whether moms will buy a product or not depending on these cups having BPA in them or not.
Good luck!!