I carry a tool roll with:
Screwdriver to fit flint jaw and sideplate
Mainspring vise
Spare vent picks
12 cleaning patches
5 spare flints
Cleaning jag
Ted Cash oil bottle
Piece of leather strap (for added grip in pulling a stuck rod or ball)
I carry a tin of Moose Snot, a bottle of moose milk, a tiny (nitro tablets) of 91% alcohol to wipe the frizzen, and a waxed deerskin bag with six feet of pre-lubed cotton ticking.
In the patchbox are a tow worm, ball pulling screw, button jag and a spare flint (wrapped in cotton tick that's pinned by the box spring so they don't rattle or fall out if the box gets accidently opened).
On the horn strap are a powder measure, vent pick (bent to hang beside the measure), and a three-hole ball block.
I also have three spare flint leathers in the ball bag (which holds up to 60 balls, but usually less).
I make the distinction between a "possibles bag" and a "shot bag" (or hunting pouch). A possibles bag is more like the haversack. Things you
might possibly need. The shot pouch is things you WILL need to shoot and maintain the gun. Food, spare socks, cookware - not in the shot bag.
My hunting pouch is fairly small, but I can still hold the fixins for 60 rounds when treking or wandering off to shoot. And, the gear to clean the rifle up afterwards.