I was thinking Steger Mukluks but the price is high for me and they really don't want you wearing them in rain conditions. Finally I came across great reviews for Chota Quicklace Mukluks. I happened upon a pair in the size I needed on Ebay and with shipping came in at a hundred bucks. Absolutely flat sole very wide with nice give to them if 2 pairs of socks are worn. I stood in the lake today draining water out of our paddle boats and no leaks. The only question remaining is traction on packed snow. May require Yaktraxs or similar if they prove too slippery.
http://chotaoutdoorgear.com/shop/product_info.php?cPath=34_37&products_id=50
Very interesting. How cold do you think they will be good for?