Missing fiducials

So I made a small error and put fiducials on the top side of my board, but not the bottom... I'm trying to drill through the fiducial so I'll have a landmark on both sides to work with, but the accuracy isn't great - anyone ever dealt with this problem before? Thanks!

I can offer two suggestions besides a drill press or mill, and assuming no digital readout for position.

1. Optical center punch
2. Use a center drill first.

You may be able to make one PCB a template.

It would be easy to stack, edge find and drill on a mill with a readout.