can you find it over the counter easily?
Cook the potato, then refrigerate/freeze...converts regular starch to “resistant starch”:
https://www.healthline.com/nutrition/cooling-resistant-starch
https://www.elizabethrider.com/guide-to-resistant-starch/
https://youtu.be/YvJGvoJtokA?si=lLVhhQ-6rbBukVW3