I'm thinking about this. http://www.amazon.com/gp/aw/d/B000YOQQFU/ref=pd_aw_fbt_sg_img_2?refRID=02QB3KHQQDQTT1C29J82

I have a Minoura seat mount.. it works good, cheap at $7 (no cage), its just heavy

I also have a xlab delta that works ok too, more of a pita to mount.

i don't really like seat mounted because I prefer to have my bag there.