Hi All!
after some 35 years of making my own full-coverage mudflaps, I have now settled on BuddyFlaps:
http://www.buddyflaps.com/The are made from 3mm vinyl and are heavy' that weight seems to be key in their effectiveness, as they tend not to blow back as much as my homemade versions made from thin vinyl notebook covers (among other things). They aren't perfect, but come much closer than the alternatives I've tried.
PlanetBike offers some shaped a bit like sugar scoops in their spares department; many of these items will fit other brands:
http://ecom1.planetbike.com/smallparts.html I love their width, but they don't come down far enough to prevent the "spray zone" from including the crankset, and their shape makes them semi-rigid...not a good thing if you snag something while semi-offroad. My ideal would probably be a pear-shaped version of the BuddyFlap, but it might have some unforeseen problems in practice.
As for small parts and SKS fenders, I have been in contact with the US office, who responded quickly and very kindly advised such things aren't available in the US market...no add-on reflectors, no replacement mudflaps, no nosecones. Nice company and representatives. I do wish they supplied small consumable replacement parts like PlanetBike does. Actually, I wish more companies of all sorts would adopt PB's "repair-reuse" philosophy.
Best,
Dan.