In ISCKON, there available a Mala called Sakshi Mala that has about 15 to 20 beads in it which you hold and count in your left hand, when you do Japa in the right hand with regular 108 Rosary and once you finish one round, you can count one Bead in the left hand Sakshi Mala (You can call it by any name of your choice).
You can conveniently prepare or modify already existing mala for this purpose.
Vinay