First off, it's not hard to find supps that aren't ascorbic acid. Calcium and Sodium Ascorbate or easily obtained, as are plenty of so called "whole food" vitamin C.
But the bigger question is, why would you need to? The studies posted in this thread both used ascorbic acid, and many of the all of the other studies and doctors that have had amazing success used plain old ascorbic acid, or one of the ascorbate forms if using it IV.
Didn't Ray Peat talk about the negative effects of ascorbic acid to Danny Roddy or one one of his KMUD guest appearances? I was also just listening to a doctor that specializes in thyroid health and he says to stay away from it. Im drinking OJ and eating certain fruits, if I can get enough C from those i'm happy since i'm already supplementing enough as it is.