What inactive ingredients do you find "questionable?" Every drug has inactive ingredients, so if by "clean", you mean a product with nothing but aspirin in it, you would have to order raw ASA from a chemical supply store and weigh out your own aspirin.
If there are specific inactive ingredients you are concerned about, even though the FDA has approved their use in that drug product, you can probably find an aspirin product without that individual ingredient if you look hard enough.