Tractor Supply has a big selection of rubber boots, in a wide range of prices; I've never bought actual boots there, but last year I bought a pair of "Sloggers" that I love - and they were half the price of a similar waterproof shoe from another garden store. (they do collect a lot of dirt in the tread, though - they don't come into the house until the gardening season is over and I give them a good cleaning, otherwise they sit on our back deck.)
