I need to replace 2 front wheel studs on my CX9 but everywhere I go (sans the dealer) only have studs that a slightly smaller where they "bind" into the wheel hub. The OEM size at the point of entry into the hub is 14.31mm and everywhere I go, the size is slightly smaller at 12.67mm

The 4 part numbers I have which don't fit are 610-468, 610-468.1, 610-568 and 610-568.1. I had all 4 parts in front of me, Doorman brand, and they where all the same size - smaller than the one I removed from my CX9...

 

This link shows the Dorman chart for studs. You'll need the knurled diameter in hundredths of an inch, not mm.
https://www.dormanproducts.com/Pages...are/index.aspx

If all the studs are this rusty, why not renew them all when you do the job. While the torque specs call for dry studs, a very small dab of antiseize compound on the threads will keep them clean. With any type of lube, do not over torque or you'll risk permanently stretching the stud. (Torquing a stud, the twisting force, includes the friction of the threads and nut face against the wheel as well as the stretch of the stud. Changing the friction changes how tightly the nuts clamp the wheel to the hub even at the same torque on the nut.)