I would suggest the Fiber gummies over anything else OTC. My RE's nurses will not let me take ANYTHING OTC besides Tylenol. That includes Tums which I know are safe.
It's possible that your OB will advise you not to take anything else either. Vitamins are generally always ok. If you still don't want to take them, I suggest natural fiber such as high in fiber whole wheats or leafy greens.