Buy a handful of the all-brass 10ga empty cases from one of the places like Track of the Wolf or Dixie.
They are not cheap, but the cases if handled carefully will literally last forever, especially with blank loads.
5 or 6 would be plenty in my opinion as they can reloaded quickly with simple homemade tools right on scene if needed.
You can use commercial 10ga hunting round cases, but everything around will be plastic now.
Loading plastic shotshell cases w/black powder makes for real mess in most instances as the high ignition/burn temp of the BP melts the plastic walls of the case (and plastic wads if you use them also).
It leaves the melted plastic streaked and stuck to the walls of the bore of the shotgun,,cannon in this case.
Plus it will make the cases themselves usable for one or maybe two reloadings depending on mfg'r. Some are worse than others.
I have found that in 12ga, the cheap Remington black cased 'Gun Club' cases do not melt and are usable but only for one loading as they are crispy burnt on the inner walls afterwards. But they do work. No melted plastic from the case inside the bore. They are the only one I've found.
I have no experience w/10ga plastics in BP.
Cut the brass cases to the length you need, or most likely you can order them that way.
Load with a light charge of FG, or FFG black powder for a blank.
You need very little powder to make a big noise.
Even a lowly one or two dram load will produce a loud report.
Standard #209 primers are used generally but make sure any cases you buy so state and that they are not 'berdan' primed.
Berdan primers are hard to find and not easy to work with for the occasional reloader.
Some modern all brass cases take a standard Large Rifle or Large Pistol primer and will so state.
Commercial over powder wads (hard cardboard) are available in the right diameter to compress and hold the powder in place.
Or common newspaper will do for blank cartridges.
Sometimes the newspaper will shred a bit upon firing and bits of it will burn so be mindful of that.
Don't attempt to make any blanks w/ smokeless powder.
Black powder can be hard to find off the shelf in most places but some searching will usually find you some.
The BP substitutes are used for blank cartridges two (many think that is the ONLY thing they are good for!).
Have fun!