I don't know what you mean by no 44-40's available. There are Henry's, '66's, 73's, and '92 replicas from Uberti, Cimmaron, Navy, and EMF. In pistols there are Colt SAA's and replicas from most of the same manufacturers, plus real Colts from Colt. Also, S&W scofields in 44-40. What do you want? Go on
www.gunbroker.com or
www.auctionarms.com and type 44-40 into the search bar and you will get pages and pages of them.
When I started CAS, I went to the 44-40 and 38-40. It is easy to reload, doesn't require anything special, eliminates blowby in lever guns, and works great with BP. UltraMax and Blackhills and 3D all make good CAS factory loads. If your shop doesn't carry it, then mail order it. Don't limit yourself to "what's in town", if I did that I wouldn't own ANY guns.