We tried the haberman and tbh it was really messy and not easy to take out and about! If you can get hold of one without much expense it might be worth a try, but in the end it wasn't worth it for us.
What did work, at around 8 months, was a soft-spouted sippy that had a similar action to breastfeeding. Ours was from Boots and unfortunately they no longer make them, otherwise I'd link. It had a removable valve in the bottom and a bigger spout than most cups. Might be worth a look?