I've had zero luck in thrift stores for boots, they always have awesome boots for women for jedi/sith but for men...yay work boots and rubber boots.
Here's where I'm getting my boots from, they're not leather but they look right and the price is good:
http://www.gentlemansemporium.com/store/001844.php
I've gotten a hold of the crown maker, just waiting on some measurements from him to see if the thing will fit even remotely. I have a stupidly large head, my BM helmet barely fits.
*EDIT* I would not really recommend these boots now that I've received mine and tried them out. They're not the worst I've ever seen, and for $50 who can really complain, but they are sloppy fitting ( in my case still over larger even though I ordered a pair that I was at the high end of size-wise). In the end I may just end up wearing my leather workboots since all you can see is the toes while walking.