You can get Bentonite and Malic Acid at the Vitamin Shoppe on 7th Ave. and 14th St. in New York. That's about halfway between Downtown and Midtown.
Any Red Subway line (1,2,3 and 9 trains) will take you there. Any Blue line (A, C and E trains) will take you a block away, to 8th and 14th. And the F train (orange) stops at 6th and 14th.
Never tried to get the other things there, but they may have them. If not there are Vitamin and Herbs shops and Natural Health stores all over the place in Manhattan. Just walking around you should see several of them :)