Howdy
When I was a kid, you could buy the High Standard Double Nine. These were 22 Rimfire revolvers designed to look like an old single action. As you can see, it has a swing out cylinder. They are no longer made, but there were lots made and if you hunt you should be able to fine one. I saw one on Gun Broker a few minutes ago.
There were quite a few double action revolvers made in the 19th Century. At the top of this photo is a Smith and Wesson 44 Double Action. This one was made in 1881. It is chambered for the 44 Russian cartridge. I only shoot it with Black Powder. The smaller revolver is a S&W 38 Double Action, chambered for the 38 S&W cartridge.
Colt made the double action Lightning revolvers. They were chambered for 38 Colt and 41 Colt. This one is the 1877 model. It was a fussy revolver and they often broke down. A year later Colt introduced the 1878 model which was more robust.
Merwin Hulbert made both single action and double action revolvers. This is a photo of a double action Pocket Army. Don't be confused by the term 'pocket'. These were big revolvers, as big as a Colt. This one came with two barrels.
Of course none of these revolvers is made any more. The High Standard was made until fairly recently, and they can still be found, but there were not the same quality as a Smith and Wesson or a modern Ruger.
The rest are only available as antiques and some of them are very costly.
Regarding reworking a single action revolver into a double action revolver, given enough money, anything can be accomplished. But it would cost a great deal. Single action lockworks are completely different than double action lockworks, and the gun would need to be gutted, and probably the frame would need to be hogged out some more to fit in a more complicated double action. It would take a very, very skilled gunsmith, and it would probably take him a few tries to get it right.