Put a pair of nitrile gloves and a couple of cotton balls in the seat bag. The gloves are great for any repair on the road so you don't get the bars/hoods all nasty from chain grease afterwards and the cotton balls are useful for finding small things on the inside of the tire that may have cut your tube but that you can't see with your eyes. You could also feel the inside of the tire with your finger, but that can lead to cuts.