I saw some on the BBGuns4less website, but have not bought any myself. They don't seem to have a good rep, but that might be more for the guns rather than other bits and bobs.
I want something very similar to that as I only have about 6m in my cellar to shoot pistol so a resetting knockdown target would be perfect. The metal ones are too sturdy for BB, I have on for airguns but it very rarely knocks down