I have a full box of WW 100 gr. lead 32-20 that says "50 rifle or handgun cartridges". The # on the box is x32201. I'm pretty sure it's out there somewhere to be purchased.
OK, I just checked.... here it is:
Ammunition To Go : 50rds - 32-20 Winchester 100gr Lead RNFP Ammo [X32201] - $40.95

And here: Cabela's: Black Hills Cowboy Pistol Ammunition