OK, this might sound a little odd considering you ask about risers, but have you considered changing the bars instead ?

Renthal High Enduro bars give a 30mm rise, but also a more natural sweep of the hands. Easy to fit (once you remove the little lug from your switchgear) and they look better.

Other than that , most riser kits specified for the Z are fine. I used SW Moto ones for a while before I switched bars.

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