I got tired of not being able to backup or move saves that were locked, so I found a way around the problem, but with a catch.
You need either:
(A) An SD Card+adapter, an Action replay disc, and SDLoad. (Google: sdload)
or:
(B) A modded gamecube that can run a custom built disk. (Google: cubeboot tools)
or:
© A gamecube mod that you can load homebrew dol files with. (Google: mod that cube)
or some combination of the above, plus unlock10.dol. I use a modded gamecube, a built disk of SDLoad, and an SD Card+adapter.
If you can do the above, the unlocker can be found in the forums at gcdev or tehskeen.
-- Acru