Those companies aren’t polluting for fun, are they? If nobody buys their products, no pollution is done.
Of course, a valid counterargument is that buying alternatives is too expensive (or non-existent, which most likely also has to do with price). And then the valid recourse is politics, subsidising alternatives, or in my opinion the better choice: making polluting products more expensive (by means of carbon tax or cap and trade).
I avoid buying concrete whenever I can…
As for stuff shipped overseas I buy US stuff as much as possible. I’d love to buy a US built and sourced computer and phone but I just don’t think that’s possible.
We avoid beef almost 100%, it’s hard to get goat but it’s my favorite when it’s available. My wife and I aren’t vegetarians but we’re pretty close.
I’m not discounting what an individual can do but no amount of individual choice will change the system enough without pressure from the top. Either regulation or real competition, neither of which are on deck it seems.