Identify a Part That Holds Glass Panels

Hey there! Thanks for posting. The piece you show here is called glazing bead. We actually sell a ton of different styles, but nothing in our inventory is an exact match for your original. I'm hoping that yours is just an older version of one of our more modern products, but it will ultimately come down to size.

For now, I've made a list of potential replacements that you can consider. We have detailed pictures and dimensions on each of their respective store pages that you can use as a reference to pick the best match, assuming one of them is a winner. 

These can be painted, yes, though I recommend asking a local hardware store exactly what type they would recommend just to be safe.