My interest in odd calibers is biting me in the butt. 16 gauge, .300 Savage, .38 Super, .44 Special, .32-20, and .410 skeet ammo.
Ballistic products in MN has fair amount of 16 gauge components. Powder Valley in KS, recently had some 16 gauge shotgun shells, seems like I remember some at Midsouth Shooters Supply. I have a model 12 Winchester 16 gauge pump with 2-1/2” chamber. Think it was made in 1924. So I have to reload it.
If you reload ammo the other cartridges can be found or reloaded. I frequent 5 different distributors that are reputable. 300 Savage brass is the only component that is hard to find on your list. I think I have a couple of rounds of brass that I got from once fired source in my order for .308 brass. If you reload 300 Savage, will be glad to mail them to you.