You can get them at any PetClub or PetSmart, etc.
I have an Oceanic 58 and it's roughly the same as the AGA 65 (though shorter by a bit) I use an old magnet cleaner that I bought many moons ago for my 37 freshwater tank with thinner glass.
I'm guessing that almost any $10 typical mag cleaner will work, no $200 magnavore necessary.
V