Ebay might turn up something. Several years ago now I found a 370-1100 lb/ft Norbar torque wrench on Ebay. According to the seller (a business), it was purchased new for a special job, used twice and then sat unused till they sold it. Looked like new. I was the only bidder and got it for $250.
Buy this Sweeney 3/4"f to 1"m... 3.5 to 1 torque multiplier good to 1000 lbs and use a lower range torque wrench.
Ebay auction number 121382502633
There are MANY ¾ drive torque wrenches on Ebay, with the exception of Neiko which claims 700 lb/ft, they all stop at 600 lb/ft. If the OP needs more than 600, its either go to a 1" square drive, or a torque multiplier.