Hello, I'm looking at the YN 560 IV or the YN 660 flash units for my EM-1 Mk 1 and an on-camera controller. I know that both of these flashes are manual. I'm fine with that. Your recommendations on the 560 vs the 660 would be welcomed. However, I do not see the on-camera controller on the B&H site. Can someone point me to an on camera controller for either of these two flash units? Thanks!