There's not a lot of reputable brokers that will have the shares to be able to short penny stocks. There's some smaller ones that actually promote it and I would just Google them and look into it but I would also be pretty hesitant as well. I know it sucks but you have to just wait for the dip and then buy. I waited for that first dip down to .55 and if you look at my post from back then I mentioned it was a buy before the run that day and I flipped personally for 10%.
By this time you should already be a millionaire. Take that money open up a larger account and you'll be able to short the hell out of OWCP I bet you already knew this.