Tang (remember Tang?) is still available online and has 100% of the anti-scurvy C! For those of us not in citrus growing climates who want to prep.
Believe it or not, citrus is not the only high content source. Many colder zone hardy crops and trees have just as much or more. Peppers and Chilies, and Strawberries for example. There are several hardy cold weather varieties of Kiwi fruit, some Plum varieties, And the native PAW PAW. The most advantageous position is to be set up for the long term.
https://www.myfooddata.com/articles/vitamin-c-foods.php
https://www.burntridgenursery.com/Kiwi-Vines/departments/156/
https://realfarmacy.com/health-benefits-paw-paw-vitamins-minerals-possible-anti-cancer-effects/