How often and how much money do you wish to throw at the issue?
There are some pretty decent adjustable torque screwdrivers and wrenches out there, but they don't give them away, and the money is probably better spent elsewhere, if you do not expect this to recur a lot.
Torque is a measure of applied force times a distance. With a little work with a calculator or online conversion app, you can work out how much weight to apply to how long a torque arm, and get very good results, if a bit awkward to apply directly.
A spring scale, or other means of measuring the pull you apply to the length of the torque arm is another method.
I get 79.6 inch-pounds. 79.6 pounds on an arm of 1 inch, or 1 pound on an arm of 79.6 inches, or some combo that results in the same ratio. We were taught this stuff in classes, as we were expected to be able to properly torque fasteners, with various extensions attached to the wrench.
For all that folks diss on the spring bar type torque wrenches (as opposed to the adjustable 'click' type), the ones we had at work always passed their calibration checks every month. Check out prices at CTire and the like, and shop around. Like as not you are looking for a 1/4 inch drive torque wrench of some form.
Cheers
Trev