Custom reluctor ring, suggestions on where to get one

I think you completely missed my point. Yes the edges are important, we agree on that. What happens is that the sensor does not trigger at the center of the sensor, but before, and it releases past center.
It is not fractions of a degree, but it is few to several degrees.

The reluctor should be low carbon anealed steel. Runout, thickness are important too, because they impact operate points.

Sensors have data sheets, that help with applications, but most are not readily available for automotive parts. You can learn from reading sheets for similar sensors used in automation industry.

A common method is to make a wheel of correct diameter, thickness, shape ... setup sensor, capture signals with digital scope or logic analyzer. From that, make adjustments in tab, and opening widths. Then verify.

Starting point in your case is knowing the precise OEM signals.