Hi Quinn,
First off, welcome to the forums. Honestly, you can surprisingly have decently luck getting "jack boots" on ebay. That was where I got my first pair, they were shipped from China, and were decent. Search for "jack boots", "jackboots" or "knobelbechers" at eBay, and see what turns up.
Here's a comprehensive conversion chart, since many jackboot sizes are in EU sizes.
