I found this 20 and 12 gauge buckshot available from Outdoor Limited. I believe they are in North Carolina.
https://www.outdoorlimited.com/shot...-buck-rb209-2-3-4-1-buck-9-pellets-25-rounds/
https://www.outdoorlimited.com/shot...bk-9-pellet-2-3-4-1250-fps-00-buck-25-rounds/
https://www.outdoorlimited.com/shot...-buck-rb209-2-3-4-1-buck-9-pellets-25-rounds/
https://www.outdoorlimited.com/shot...bk-9-pellet-2-3-4-1250-fps-00-buck-25-rounds/