my friend wore out her bobbin racer/holder by using NON janome bobbins..in her New Home Janome.
And yes, i am sure that others have had no problem using bobbins from joanns..but why risk it.
spend a little money, and get the prewound package of 12 for around 9 bucks from the dealer..use them up, and then you will have the bobbins to fill yourself.
and you will love treating yourself to the prewounds!