Converting 7-Segment Display output to binary
The 4511 IC is a standard component used for driving a 7-segment display.  It takes a BCD input and provides the output signals for a 7-segment digit.

I'm not aware of any standard IC that does the opposite conversion.

The best way to do this, as @Decapod mentioned in the comments, is to do this in the PLC logic, editing the program to use 4 new output points.  However, if you don't have editing access to the program, or you don't have 4 spare outputs, this might be difficult.

An alternative is to use an intermediate controller to do the conversion.  An Arduino or other microcontroller is inexpensive and could work.  Another alternative is to put in a small PLC just for this purpose, which might match your voltage signal requirements better and are already packaged for an industrial environment. (The Click PLC from AutomationDirect is one example.)  The programming of these are quite simple, and I have a hard time believing that you would be able to purchase a pre-built one-purpose module for less than the cost of one of these small PLCs.