k5 memory card

Hi to all k5 owners,

I am new to this synth as well as to this forum.  I recently purchased
this synth keyboard used.  It did however, not come with a memory
card.  I am interested in creating some of my own sounds with this
piece of equipment.  Is the card necessary for this and if so, where
can I get my hand on an aftermarket card?  Any advice from users would
be greatly appreciated.  I hope that I did not get in over my head by
making this purchase as I am a novice to the greatest degree

Kevin