Go to spencers and hot topic, tons of baby / father items he will get a chuckle from. I got my child's father how to books, a baby medic care kit, and just items you'd find in a diaper bag like nuks, a bottle, baby clothes, bath items and blankies / burp cloths but they all have writing on them that reference daddy in some way. Hope that's helpful :)
(If you are formula feeding) You can but one of those little containers that people put premeasured formula in for on the go. I know some dads that can never figure out how much formula to mix with the water lol.
I should make one of those! Someone in another board suggested a tool belt with diapers and what not in it, so I think I'm going that route. Just need to decide what all to put in it.
I've seen a onsie somewhere that hand instructions written on it that showed the dad where to put the arms, legs and head of the baby lol