You can buy a .750 low profile gas block here. Micro pistol gas tubes are 1.5 inches shorter than pistol length gas tubes. Buy the pistol length gas tube here and cut it to make it fit. You can confirm the length you need by test fitting it and the BCG and attached gas key and if the bolt won't seat all the way in, take a little more off the end of the gas tube. Remember, the gas coming out of the tube pushes the bolt back... that's it.
Try KAK Industries.
You need a micro gas tube. KM tactical and delta team tactical have them.
look for or search for "micro gas block."