A friend modeled this support for me off the old one. It holds the center rail to the rear of the cabinet.

I wouldn't even know where to search for these so I figured I'd upload this in case anyone else has a similar problem.

I uploaded an STL and CATproduct file in case anyone needs to remix it.

I used Adaptive Cubic infill from Prusaslicer @ 20% with 3 perimeters. It seems strong enough to support the drawer. I'll post an edit if there are any issues.