Black plastic piece on end of operator arm

Hello!

Thank you for your patience during this busy season. I'm afraid I don't know what it is that you need. I would need to see a photo of the part in question to compare to our inventory. 

That appears to be the slide on a hinge. These are unfortunately not sold separately and if yours is broken then you will need an all new hinge assembly.

My top recommendation is the 36-048. This may work for you as long as you replace both sides at the same time. Check it out and see what you think.

Detail of 36-048