@JimB Thanks for getting back to us with some more details!
We have a couple of options that could work for you. If you want to mount directly to the rear hub take a look at the Axiom Cycle Gear Streamliner Rear Bike rack. If you're not planning on using panniers, you could consider a seat post bag like the Co-op Link Seat Pack or the Revelate Designs Terrapin System seat pack. They mount easily under your seat and can provide a versatile way to carry a few extra items.
Hope this helps!