At one time Freedom Arms had a black powder C&B .22 revolver. And there is this very similar .22 C&B from NAA: North American Arms Companion Cap and Ball Black Powder Revolver #11 Percussion Cap Equivalent to .22 LR Caliber Wood Grips Stainless Steel Finish

I don't know of any others aside from the Ruger which could be considered modern, but there is an abundance of replica Colt and Remington C&B revolvers. As a carry gun, I think a replica Colt Model 1849 (.31) C&B would be excellent, albeit a little lacking in power. I have an original one of those, but do not shoot it much. A conversion of a more modern DA revolver to C&B is certainly possible, but I have no idea how it could be easily loaded after the first five or six shots have been fired. And there were some early British-designed C&B revolvers in double action.

I remember some postings here regarding some of the more draconian European gun laws (don't remember the country) which indicated that in at least some countries, a replica C&B revolver is considered as modern, and in order to be above the law, all black powder handguns had to be manufactured prior to 1890 or maybe 1888 - I don't remember.