You can find small quantities of little plastic bags of any size at a craft store like Michael's, usually in the bead section. I use little tiny ones for salt and spices.

I don't know what the deal is with hot water and freezer bags. Freezer bags were designed to hold food that has been blanched in boiling water and then placed directly in the bags. By the time you get the pot of boiling water off the stove and pour the water first into a cup and then into the freezer bag, the water is no longer anywhere near 212*F even at sea level. Certainly not at 5,000 feet elevation where I was the last two nights! It will be about the same temperature as the blanched veggies you are preparing for your freezer.