Many Piper aircraft have the same problem. The sun visor catches lose to stability, because the UV effect allows the plastic to become porous. These Piper Sunvisor Catches are made from a blended poly-plastic with a UV additive that will prevent UV corrosion.
A set contains two pieces with the required plastic rivets. They are available in white and black (used in Piper PA-38 Tomahawk). The set for the Piper Tomahawk contains two extra rivets.
I was glad to replace these catches, and they are quite ok. But they are a bit too tight for the sunvisor plastic stem... it is a bit hard now to get it out from the catch... there is a small risk to break the plastic stem when trying to move the sunvisor.