44 russian, 455 webley, 38 spl are all available, though may be loaded too hot for your preferences.
I'll also suggest reloading. For what you're going to pay for factory ammo you can load yourself.... at lesser cost... with greater control over loads.... and shoot a far wider array of calibers. For antiques it's pretty much a no brainer. Lee's hand press kit is a great option for starting out. It's a small kit, affordable ($70) and easy to use. Not the fastest, but really has the advantage as far as being easily packed up and stored, transported etc etc. You'll need some other stuff such as a scale (they can be found for $10 at gunshows), powder (avg $25-$40/lb), bullets, dies (avg $30-$60, more for special made dies), primers ($5) and brass. Factor that all together and you're running at about 3-4 boxes of factory ammo.... except that your cost to get started reloading includes several hundred rounds worth of materials... so you've essentially bought a reloading setup and ammo for the cost of 4 boxes of factory stuff.