I think the fact that the root of your question is how to "make" someone want something he or she doesn't want is the thing that disturbs me most about your question.
His feelings don't seem to matter to you very much. You want a baby, so you're trying to make it so that he does too.
Now, you could just make small holes in his contraceptives, or lie to him about being on the pill. That'd achieve your goal.
Reverse the roles for a sec. Let's say you didn't want any more, but he did. Doesn't matter that he'd argue it'd be him doing the overtime, him looking after them both when you are sick or away, him crunching the numbers to make sure the finances work out and all you have to do is give birth to it and feed it.... you would resent the mere suggestion that you accept that kind of responsibility when you don't want it.
In fact, IIRC women want the right to not be mothers without having to explain themselves to anyone, and rightly so. Please give men the same courtesy.