Ive done some investigation on these strips. I do suppose you mean the plastic strips with sticky tape on one side and the "magnet" on the other.
These are NOT magnets though but something that we call "weak iron". This piece of metal is enough to influence the electromagnetic field for edge convergence correction.
In theory pretty easy to reproduce....just need some of that plastic material, weak-iron and double sided tape.
However, I prefer to get them from old TVs.