Sunshades and the likes are not mentioned explicitly, however, there is the basic rule in almost every FOM that a lookout (also in cruise etc.) is mandatory.
Worked for an airline where even the use of explicitly described sunglasses was mandatory.
Using the self-manufactured (papers / maps) sunshades, this includes also the ones available in shops for car windscreens, may lead to overheating of the window, serious implications may be the result.
How far, however, some colleagues protect themselves from the big yellow heater you may be able to see when scrolling through pictures on
this website, just search in 2005 / 2006 for B737-400 landings in ORY, you may be impressed. Sorry, do not have the direct link available anymore. Needless to say that this colleague is not with this airline anymore...