DXD????????????????????????? QQQQ and DXD are 2 TOTALLLLLY DIFFERENT ETFS. DXD is the 2X ULTRA SHORT DOW 30 ETF As for the original poster, you dont want to short QQQQ, BUY PSQ INSTEAD. PSQ PSQ PSQ NOT DXD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I prefer QID as the inverse etf to short qqqq's. If your broker doesn't have shares available to short, just buy this. Also, ditch your broker, if they can't find shares to short on such a liquid etf, they're not worth using.
Or as an alternative you can short the Single Stock Future on the QQQQ ETF in either a 1000 multiplier or a 100 multiplier. Both have two sided markets being made by marketmakers. Best