Where to buy replacement stem faceplate?

[Dionysiac]

How can I order a replacement handlebar stem faceplate? Can I order another brand faceplate or are these proprietary?

[Radio Runner]

Gonna be hard to find an exact match. Most likely going have to buy a new one entirely. There are lots of stems on the market and you should be able to find one in the same dimensions pretty easily if you know what your looking for.

[tacomanatx]

Are you talking stem cap?  They are all pretty standard now days and a simple hex key swaps them out.
https://kustomcaps.com/

[Radio Runner]

Are you talking stem cap?  They are all pretty standard now days and a simple hex key swaps them out.
https://kustomcaps.com/

Doubt it, Described as " faceplate" makes it sound exactly like the front of the stem not the bearing preload cap.