There are several synonyms for the phrase "paragon of straightness." One such synonym could be "exemplar of honesty," as both phrases indicate a person who consistently displays a commitment to morally upright behavior. Another possible synonym is "model of integrity," which emphasizes the idea of acting in accordance with one's principles and values. Additionally, the phrase "paragon of uprightness" could be used in place of "paragon of straightness," as both phrases convey the idea of being morally and ethically sound. Overall, these synonyms all serve to convey a similar sense of unwavering commitment to honesty and ethical behavior.