Welcome, I can personally recommend the Rapid Transit 19L recon tank bag, has a bunch of pockets, and plenty of storage space. It fits the bike great
http://www.rapid-transit.com/Products/Recon19.htm
FEATURES
Magnetic tank bag
WIND & WATER RESISTANT 1000D nylon construction
Scratchguard rubberized contact fabric
Magnetic mounting system
Integrated tank protector
Backpack convertible
Hydration Ready ( optional bladder )
Audio Ready System
Map window, Cell phone & Eyewear storage
Rain cover
Reflective stripe
40cm x 26cm x 18cm storage (18.7 Liters)
15.8” x 10.2” x 7.1” storage (1144 cubic in.)
My tailbag is a discontinued Rapid Transit, it's expandable, and has a lot of storage space.