I just bought a pair of 3421 and converted them to 3421SA's by replacing all of the metal gears except the main output gear with nylon gears for a JR 321 servo. The nylon gears are 3.95 a set and you get two sets of gears in one package. Little bit of a hassle and a few more dollars, but if you really want a 3421SA (I did), it's still possible. As I understand it, the other SA servos can also be created the same way but I didn't have any problem finding the 9411SA and 8411SA. I believe the nylon gear set for the 9411 is the 911 and the 8411SA would be the 811 gear set. You can also get the whole SA gear set which includes the alloy output gear but they cost quite a bit more.
Verne
ORIGINAL: Ryan Smith
Vince (and all),
Things have been rather busy around Horizon and I didn't want to pester with something that wasn't super important, however the 3421SA and the rest of the SA line of servos for that matter have been discontinued like Jon said. This is due to diminishing sales and the need to slim down the JR line some. I'm just as sorry as everyone else to see this happen, but at least we know.