Wow, I'm a FTM and I've been in maternity pants since 12-13 weeks! I don't know how I would make it through without them, even the belly band was a pain to me. And if you're going to spend $15 on a belly band, might as well get a pair of pants on sale at Kohl's or Old Navy.
You should check out your local freecycle board. I posted on mine asking for maternity clothes and got 3 bags from a woman in my town. They were all in good condition (since they're hardly worn) and I got some really cute stuff for free! You could also ask friends and family if they have anything you could borrow - I know some people save them for their next pregnancy, but if you promised to return them you might get some that way as well.