I am interested in marketing a handheld consumer electronic novelty
device of a kind I've seen before.  It would be a small box with
several buttons that produces short phrases and sound effects when
buttons are pressed. I'd l like to be able to customize the phrases.

I would like to receive a list of manufacturers who make such devices.
I assume that no additional design will need to be done, but if this
assumption is wrong, I'd like to learn what that design will entail.

I've never done this sort of thing before. I would like to receive
broad advise on dealing with the manufacturers. A great answer would
also include rough estimates of the cost of such devices and typical
delivery times.