"Real" wheel diameter
Even if someone had a magic database of actual versus nominal sizes for tires, they would need to know what tires you have now and their actual inflated size on your rims to answer.

The best answer is yes, probably there is a nominally 700x32 tire out there that's smaller inflated than what you've got. But, two issues there: tire manufacturers have gotten much, much better than they used to be about accuracy in size labeling, so finding that tire would now be a challenge. Secondly, manufacturers often correct badly size-labeled tires pretty readily, so even if there were a good recommendation out there, it would be a bad question for an SE site since it would be a product recommendation that's highly subject to change.

A better approach may be just get an accurately sized 700x30, which is an existent albeit not super common size.