They sell sippie cups at Wal-Mart that have a soft bottle like tip, only the tip is larger than a bottle and they look more like a sippie. They are a Nuby brand. Very inexpensive, in case he doesn't like them. $1.89 or so.
They are generally in a large box display near the infant stuff & come in lots of colors.
It may be an easier transition for him since the tip is pliable material instead of hard plastic. Plus, they are shaped to be easy to hold for small hands.
Good luck, and i agree, I wouldn't rush it. ;o)
*hugs*