There is a second way
I have faced the same issue on several occasions. In my view it's acceptable to drill out the rivet holes in the nutplate to 1/8" and use standard size pop rivets. The issue for me is which is stronger, a thinned edge of steel with a standard pop rivet or a bigger edge of steel with a very puny rivet? In either case, all you are asking the rivet to do is to keep the nutplate from turning when you apply no more than 25 in-lbs(?) of torque.
I invite others to politely flame me for this, but it is a possible way to go.
When faced with a similar problem in weak substrate such as the wingtip under the lens, I used JB Weld epoxy of the type that is like stiff putty and mixed in slices cut from a roll. It sticks and hardens very well. That was for holding #6 or #8 machine screws, not bolts, though. The JBW holds the nutplate, not the screw itself. Be sure to put release stuff on the screw and put it in place until the epoxy hardens. BTW, I used something like that for the two thin screws that hold the strobe/position light to the aft end of the rudder bottom so the heads are on the outside.
