Jeff: There are lots of options now for low pressure loads until you start handloading.
Polywad 'Vintager' http://www.polywad-shotgun-shells.com
Eley subsonic/low recoil http://eleyshotshells.com
ARMUSA 'Vintage' http://www.armusa-performance.com
Kent http://www.firearmservice.com
RST http://www.rstshells.com 570-553-1651
I understand RST will sell a mixed case to fit your needs.
Cabelas has Gamebore shells at about $8/box also.