ARMUSA ceased operations last fall but excellent options remain.
Polywad 'Vintager'
http://www.polywad-shotgun-shells.com 800-998-0669
Gamebore
http://www.gamebore.com/index.asp is distributed by Target Loads USA 217-243-3727 Jacksonville, Illinois
RST
http://www.rstshells.com 570-553-1651
And more 12g low recoil loads are available, which I would be perfectly comfortable using in a 2 5/8" 12g chamber:
Nobel Sport now has light 12g 1 oz and 7/8 oz and 20g 3/4 oz loads
http://www.dkgtrading.com/nobelsport/lr1.htmlRemington 7/8 oz. 'Managed Recoil' load
http://www.remington.com/products/ammunition/shotshell/target/managed-Recoil_STS.aspBy Federal for MidwayUSA to the following specifications:
7/8 oz load Muzzle Velocity: 1200 fps Chamber Pressure: 5000 psi
http://www.midwayusa.com/static.exe/getstaticpage?page=11120061_page.htm WinLite Low Recoil
12g is 28gm (1 oz.) at 980 fps
20g is 7/8 oz (just more than 24 gm) at 980 fps
http://www.winchester.com/products/newitems/whatsnewcontent.aspx?productid=52