With mismatched feet (my left has issues fitting into a 12, while my right fits comfortable into an 11) is really hard for me. You're not alone.
I use Payless. Decent selection in large sizes, good prices, but not always the best quality. I knew I'd have to make a sacrifice somewhere though, unless I wanted to pay over $100 for a decent pair of boots in my size. I got a nice pair for $30. Not the best quality, but they're shoes, they fit well enough, and they didn't cost a bomb