Bet if you could get replacement compartment covers someone could adapt a small bag to it. Thought I had seen a water bottle holder someplace but can't find it now. Also Captain Itch might be able to help with a bag.
Ron,
I contacted Captain Itch, and they said they didn't make anything like this and suggested maybe finding an Amish vendor who could make a one-off for me to my specifications.
I'm using the left fairing pocket for keys and wallet, and keep my phone plugged into a charger in the tour pack now. I had really wanted a pouch like this, but have pretty much changed my mind since then, due to cost.
The below picture are two different Harley Sissy bar bags, $99 each. I really liked the one on the left, but they're both too wide to fit on the lower nicely. Either one would look nice on the lower if they were a bit smaller.
I say if you're in the market, buy a Renaissance pouch, get some Goop glue, and bond a Harley Medallion onto the pouch and you'll be all set, plus for less money than the HD sissy bar bags.