I always get my perlite 1/4 inch size and shop for other substrates like coconut husk chunks in 1/8 to 1/4 inch size from my local marijuana growers supply shops. They always have a cool assortment of substrates, and gadgets and a myriad of "magic fertilizer elixers" to look at. And grow lights too. But they have been my best source for a "good for bonsai size" substrates of different types.