I had (have) a Schuberth S1 with the drop down sunvisor. Loved the sunvisor, so-so on the helmet.
Last year got a new Shoei Qwest, way better helmet all round apart from no sunvisor. Missed it a lot.
Various talk in other circles about Sunax inserts, people generally like them but silly money for what they are (IMO), so I did a DIY version.
Basically took an old visor (many years old), made a card template to experiment with the shape, then cut an insert from it using tin-snips (polycarbonate is tough stuff and cuts with snips nicely, it won't split/crack - if it does crack it probably isn't polycarbonate). Then applied some window tint film, got a length of shaded stuff off fleabay for around £3.
This is it fitted.
I like having the shade without actually looking through the tint, especially useful in much sunnier climes (Mediterranean etc), set the height to suit your taste. It slips between the shell and lining, just gently ease it in.
Internal sunvisors are nice, but I'm happy with the DIY fix for an otherwise nice helmet.