The poll being conducted in this very thread meets the one criterion that you've specified. The certainty that not everyone who has responded to this poll is from the same state or the same local area makes it a “national” poll. Admittedly, the sample size is awfully small, but you didn't specify anything about sample size. In the time that I have been watching it, the results have fluctuated somewhat, between slightly less than 60% and slightly more than 70% opposed to the background checks. At no time has it failed to show a solid majority opposed to the background checks.
The sample size is too small to solidly make a claim that this reflects the opinion of the American public, but it is certainly enough to refute the lie that you keep repeating over and over again about there being 90% support for these background checks. It's a lie, it ha been proven to be such, and if you wish to retain any vestige of credibility, then you will stop repeating it.