Amazon will ship to Poland (but some of their marketplace sellers won't). Some ebay sellers will ship to Poland and some won't.
Your best bet is to simply use a shipping agent in the USA: the website/seller posts the item to the shipping agent and the shipping agent then send them on to you in Poland. That's how I do it. The total cost is less than getting the seller to ship direct to Poland and you aren't limited to only sellers who will ship to Poland.
You can buy from Amazon in Poland. It's shipped from the UK (or it is whenever I use it).
Stuff from amazon? That would certainly be helpful from a tax viewpoint.