I'm in the same boat, but with a 10 mo old.
I bought a Born Free sippy cup and let him play with it with filtered water in it. When I think of it, I try to pump some BM as well. He typically chews on the rubber spout (I liked that brand because the spout is flexible), but that does release the contents so I figure, practice makes perfect. And on occasion, he does seem to suck on it. I even have squeezed the nipple while in his mouth. He does end up with water on his neck/chest, so it's less messy than BM.
I'm bad about not remembering to give it to him daily though, so it's my bad that he's not taken to it yet.
