Mine isn't for sale, but I can confirm that the Defiance action wrench works on my impact 737 actions perfectly. There's a Defiance wrench in stock at Area 419.
My Defiance Wrench fits about the same as the bolt does in the Impact Action. It also fits about the same as it does in a Defiance action. I torque my actions to 55 lb/lbs and have used the wrench dozens of times without problems on both Impact and Defiance actions. Maybe if you like to torque to 100 ft/lbs or more it might make sense to get the exact wrench but this method has worked for me.