There have been a couple reproduction .32-20 SAAs on the market in the past 20 years or so.
And yes, Winchester at one time loaded a line of Hi Speed cartridges in .32-20, .38-40, .44-40, .45-70, and maybe a couple of others.
The .32, .38, and .44 were designated SOLELY for the Model 1892, and the boxes had red warnings printed on them.
The .45-70 was solely for the Model 1886.
Back then, as now, people would ignore the warnings. Such ammo would destroy an 1873 Winchester or an early Colt SAA, and wouldn't do more modern handguns any good, either.
Here we go... A link to a picture of box of Western ammo designated specifically for the Model 1892.
http://www.rtgammo.com/3220hvSX18488.jpg
That box is post 1922, which is when Western introduced the Lubaloy bullet jacket to replace cupronickel.