I am in agreement with marmotslayer on this;
The problem for you is that powder flask. That will require a larger bag, maybe with a separate inner compartment to hold it. You might want to consider using a powder horn.
Cylinder flasks are fine for bench shooters, and they work OK for some when used in a belt hanger, but a horn is much more convenient when shooting from the bag in my experience.
Your preferences will be your own when choosing a bag. Some folks like 'em big, some like 'em small, etc. It all depends on what you want your bag to do and what works best for your style of loading/shooting.
A smaller sized bag with one inside pocket of about 4" square has come to be my personal preference. I also like a gusset which tapers toward the top of the bag and ends an inch or so below the opening. The tapered gusset helps keep the top of the bag from flopping open while still giving plenty of room in the bottom. The main compartment measures about 6" wide x7"-8" tall. (I have several.)
All of the small tools that I need are carried inside of the small pocket on the inside back panel. Jag, worm, screw, screwdriver, and extra flints.
A handfull of balls are thrown in the main compartment loose, no separate ball bag. Otherwise just a small priming horn and an antler-handled t-shaped short starter are carried in the main compartment. On a woodswalk the priming horn usually ends up stuffed in the front of my shirt.
I tie a strip of ticking to the strap of my powder horn for patching which will be cut at the muzzle. On a woodswalk or range shooting I only use spit for lube. When hunting I will use a greased strip of ticking that I carry in a small well-greased deerskin bag which also rides in the main compartment of my shooting bag.
My powder measure and a vent pick are attached to the strap of my bag by leather strings. When not in use the pick is stored in and back out of 2 small holes in the strap, like a single stitch. The measure rides inside at the bottom of the bag.
Enjoy your search for the perfect bag for you. :thumbsup: