I identified the parts I would need online, shopped for price and delivery, and ordered what I needed. I bought the support arm mount assembly and decided to replace the spray arm and tube as well.
Installation was straightforward, although it took me a couple of tries to get the spray arm mount oriented correctly because it is angled to allow the spray arm to miss the deeper glasses channel on one side of the upper rack in the dishwasher. After clipping the arm support and the tube support in place, I installed the arm and tube and was finished.