Kami, Dozen was made to order on Trigger's webshop for a couple of weeks, and the BD set is available anywhere in Japan.
Looks like there's also:
The Battle of Geekboat ONE - production art
Saito Kengo animation works - genga from Promare
Hiroyuki Imaishi artbook #20 - his Promare stuff
Like anons say, those and the rest were sold at C96 & C97. I have K,D so far, another anon posted a few pics of that before. If they don't ever mass-produce a huge official 'Art of Promare' book then in the future then I may buy one of the auctions that have the comiket books in one bundle, jew prices be damned.>>3429965
Most otaku go to Comiket, it's easier to print a couple hundred copies and hand them out rather than deal with store distribution or shipping from websites. Plus some of these were just "fanart" even if they were done by the creators.