Take a look at deribit.com. They allow shorting through their bitcoin futures and options. The entire platform is bitcoin, which is pretty neat.
Be sure to take a look at the elliott wave count to see where we are and where we're likely headed: https://steemit.com/bitcoin/@stocks29/bitcoin-bearish-case-elliott-wave-update-price-is-progressing-as-expected
Awesome, will get over and take a look.