You can buy or rent these indigo-dyed costumes around August in Aomori, Japan or online at Homura Matsuri. They're damn near impossible to pick up secondhand or used unless you know someone. I picked mine up at Zenshuji for cash :p
The official kit includes:
-花笠 [はながさ] or hanagasa (flower hat)
-浴衣 [ゆかた] or yukata (summer robe)
-襷; 手繦 [たすき] or tasuki (sleeve tie)
-しごき帯 [おび] or shigoki-obi (soft belt)
-お腰 [おこし] or okoshi (underskirt)
-腰紐 [こしひも] koshihimo (waist cord)
-手拭い tenugui no mame-shibori (polka dot towels)
The diagram above includes a velcro 'magic belt', but they're made of non-slip rubber and non-breathable polyester so they instantly add 10 degrees. It's been a cool summer, but I personally didn't go this route. This often comes standard if you own kimono accessories. You can used a contrasting koshihimo as well, or a hanhaba obi if it doesn't restrict your movement.
Common motifs for haneto yukata include:
-the words 青森ねぶた祭 'aomori nebuta'
-warriors
-bijin or beautiful women
-bells on cords
-flowing water or waves
-bunny rabbits (because 'haneru' means bounce)
It's common in pictures to see people wearing non-standard costumes (like regular non-haneto yukata), as long as they were dressed 'properly', but I think it defeats the spirit of the float. Plenty of volunteers were wearing only the 2010 Nebuta shirts. Otherwise, you can always join in at the end of the parade on First Street.
