Assuming "black-tie-ish" (a description with which I'm unfamiliar) means something akin to "black tie optional," just wear your navy suit with ordinary suit-appropriate shirt, tie, etc.
I'm 100% certain that various celebrities routinely mix business suit and tuxedo gear, and I'm equally confident that some people here on SF think it looks good, but I'm telling you that it's not a traditionally approved practice. So if you care about traditionally approved practices, there's your answer.
Oh, and there's nothing inherently wrong about wearing a navy blue tie with a white shirt and navy blue suit. Don't worry that the tie is of similar hue to your suit. It's okay.