Buying on Pesach

Question

I've heard Rabbanim say that items that don't need hashgacha for Pesach and are permissible, must be bought before Pesach (so that the bitul concept can apply) and are not permissible to be bought on Chol Hamoed. The Items on your list - is it permissible to buy them on chol hamoed or must they be bought before Pesach?