If I may,
http://www.atthefront.com is a WWII re-enactment shop site. I can PERSONALLY vouch for their quality as I have purchased a WWII GI uniform from them. They may seem pricy but after weeks of shopping around they are the best price for the quality you get, which may I add is amazing.
You will easily find your boots there. And if not try
http://www.soviet-power.com/product.php?cat=24&PHPSESSID=4b296b2259d44e23eda9b3f9e3662b01Hope this helps you.
P.S. At The Front may take some time to get what you want back in stock as they make just about everything in their own ''factory'' using real issued gear as a reference. But their products are immaculate.