Corner brackets internal to bifold door frame.

Are there replacement parts for the internal bifold door frame brackets that house the pins. It appears these brackets are removable due to the philips head screws. The bifold door pins have worn out the plastic pin housing brackets causing the bifolds to sag when the bifold doors are in the open position. If they are replaceable I would like to replace all four of the brackets on both bifolds in addition to replacing the old pins with new ones. I have included a picture of of what i believe to be the stanley bifold number. Ant help would be greatly appreciated.

Thank you very much for your help. Ordering these parts has saved me from buying new bifold mirrors and for the size if bifolds I have is around $500.

Thanks again.