NAS1097AD Flush Shear Rivets are more commonly referred to in maintenance circles as "oops" rivets because it's just what you need when you accidentally make your rivet hole too big. Their smaller head diameters are exactly the same as an AN426 flush rivet that is one size smaller. So just drill to the next larger size, then use one of these rivets and no one will be any the wiser.

The 3/32" diameter rivets are also perfect for installing nutplates as the smaller head virtually eliminates the need for countersinking. Just use a hole deburing tool to clean the edges for a perfectly flush installation.