Can't do better than inov-8. If you want so really good advice in equipment for ultra's contact the guys at www.likeys.com the owners Martin and Matt have a lot of experience competing and organising ultras and supply a lot of ultra specific equipment at a good price, including inov-8 kit.
I've got the OMM 25l http://www.tiso.com/shop/omm/classic-marathon-25l/?_affid=99&_cid=1 which is fantastic and is regularly used for running to work. I wish I'd known you could ladies specific ones. Adjusted to the extreme, it is fine for the winter, but just a little loose for tee-shirts/vests in the summer.