Quoted:
If you don't need it to be low profile, check out the Paladin Machine version.  They make a 3-way lever version (off, low, high) to your specs.  Basically they are built to order and you spec in the gas block diameter as well as the gas port size.  The low cuts off 20% of the gas for shooting suppressed.  It is only $60.  Now the down sides.  It isn't the best finished product and is set uniquely to 1 gas port size.  It also only comes in a set screw model (I perfer a clamp on version).  Lastly, you have to cut off .9" of the gas tube and it attaches by set screw as well.