I've found it extremely difficult to find anyone with accessories in stock. In Australia, BMW has bugger all parts available at this point. The same can be said for Touratech and Wunderlich. I've tried the US and the story doesn't seem to be better there either.
Anyway, I managed to get (1) A Large BMW Tank Bag, (2) BMW Headlight protector, (3) BMW Small Softbag (rear), (4) Hepco & Becker Pannier Removable Pannier Racks, (5) Black GlobeScout Panniers (45L + 35L) including carry handles and inner bags, (6) Cruisin Comfort Sheepskin Seat Covers, (7) Pivot Pegz (a version for the GS LC haven't yet been made, but the GS800 version seems to fit so far).
Oh and (8) I shelled out the extra $ to get the BMW GPS. I still haven't worked out whether I like it more than my Zumo 550 or whether the BMW integration is worth the extra money over the Zumo 660.
Lot's more to go - crash bars, radiator protectors, bash plate, side stand enlarger, auxilliary lights, probably higher windscreen, may be a 'rally' style seat, etc.
Adventure is discomfort recounted at leisure!