I believe a ball extractor was only issued to a squad of 15 men, so it isn't necessarily needed.
For brushes, I have no references, not sure if there actually are any...
What I am using is a WW1 french brush, and whip to clean clothes and shoes. You can find these on French ebay and declampe.net.
Same goes for the button polisher.
Shaving razor, just search on ebay, there should be plenty.
I bought a pack of like 50 copper brushes on amazon, shouldn't be a problem to find.
For whitening, just get some pipe clay, or white powdered chalk. Should be easy to find on amazon or ebay. There is no need for both spanish and another form of whitening. On campaign they most likely wouldn't have whitened their belts anyway.
If you actually plan on whitening your leather works the historical way, use a mixture of chalk and milk, or use some kind of modern paint. Both pipe clay and spanish are not very good for your belt, it will eat it away.
The brush for the whitener... People would get these, but there are a lot of accounts of people actually loosing them, or throwing them away. If you have some old ragged cloth you can just use that instead of a brush. Its just as historically accurate and it doesn't cost a whole lot.
Linen cloth, amazon. Just buy a pack of them for 3Euro.
Wire wool is not accurate for the time. Buy a polishing block from MC Farthingbowls. I have one and it works really well.
You should add some stuff to start fires with.
You know, stuff like this small mushroom that grows on trees. (I forgot its name and I am to lazy to google right now)
You can also get a firestriker set, although I never quite understood why a infantryman, who has a musket would get a flint and striker. The musket is the perfect portable firestriker...
Anyway, if you want a fire starter kit, either search on ebay or add "Frank Grenadier" on Facebook. He sells those.
I don't know how you plan to sleep and eat, but maybe you should add a blanket or two? Also, especially on campaign events its useful to have cooking gear and a cloth bucket (for safety)
What about stuff to roll cartridges, and fill them with? Not really needed, but I put that in my pack because it is quite useful to have. Not necessarily 100% accurate though.
About shoes... There is this Czech guy making high quality replica shoes. But I forgot his name and the website link. Contact vince on facebook, he ordered a set from him, maybe he remembers.
A couple of days ago, I packed my backpack just to see what I can fit in there and how I can pack it properly.
Ignore the cloth bucket and the brown strap. I will replace the brown strap with a white strap once it is time, and because I don't know if it is accurate, but still need it for safety, I lhid the bucket in side the pack (after the pic was taken).
This is how I would pack it if I don't want to wear the greatcoat. The blankets simulate the greatcoat. I would simply roll the blankets inside the greatcoat and then strap it on top.