Triphala & haritaki both are the natural laxative. If constipation is in early stage, you can consume Triphala powder but in chronic constipation you can consume Haritaki powder. Both are the best ayurvedic medicine for constipation. You can go with any powder as per constipation level.
You can also order from amazon with the following link
Link for Triphala powder : Buy Triphala Powder
Link for Haritaki powder : Buy Haritaki Powder