There are so many places that carry oversized sunglasses. You ask what is the best place, it is really hard to tell. I even don't know where you live. If i were you, i may bought a pair from a eyeglasses shop that nearby me. If it is too expensive, i may try to find cheaper one online.
I love oversized shades. Actually, due to the increasingly popularity of online shopping, it is strongly recommended you to take a shot to purchase shades via internet which can not only assist you to save much money compared with brick-and-mortar stores, but a wide variety of types and designs are available as well. Here I recommend Firmoo and coast.com, both of which offers ''free eyewear'' activity. Besides, the custom service is professional indeed. And the most impressive part the visual-try-on system, as a sunglasses online veteran, which is the most interesting section I am fond of.