.405 Brass and ammo is definitely available, just expensive! So far bullets are in pretty good supply, both Hornady and Hawk, to name two sources.
If you're craving a .460 S&W single shot, then the Miroku is probably a good option. The Ruger .460s command big premiums, especially the ones with 22" barrels. Ruger has also made a run of .450 Bushmasters in the #1, and some of these are out there for semi-reasonable prices, but they are in the stainless & laminate wood models. The .450 Bushy of course also uses .452 bullets so a wide variety are available. .450 brass is readily available. The Number One in .450 is the only one that came from the factory with a threaded 20" barrel, so it is also set up well to run a can. That's what finally got me to buy one.
And I am with Pappy - the Low Wall Winchester, in modern steels would be awfully interesting (and effective) as a lightweight .30-30. I've thought about getting a .22 Hornet or .223 Low Wall rebored to .30-30
I’ve seen some new-production LWTHs in .357 recently. One of those could be rechambered to Max or maybe even the Buckhammer with some additional work on the extractor.
As best as I can remember, I have five “deer rifles” that haven’t made their bones yet, so it’s doubtful (not impossible!) I’ll be tackling such a project, but I’d love to see yours!😛 I’m full of good ideas, and sometimes something else…….