Barkuti
(Barkuti)
6205
Hello! :-)
Here is a related thread about the Nichia NV4WB35AM. Besides this product page at Nichia, with datasheet here, which lists an absolute maximum continuous forward current of 1800mA, Agro posted a related output graph:

The max recommended current for the NV4WB35AM in the graph curves is 2500mA, this data is wrong according to the datasheet.
Both NV4B35AM peaked at ≈4.2A.
So we have 1800mA as maximum continuous current in the datasheet (max 2400mA pulse), and according to the above test 4.2A as absolute maximum current, with declining output beyond that.
With this in mind, any of the currently available 3A 6V XHP50 drivers (like this one) are a perfect fit for the NV4WB35AM. I'd love it in 3500K or 3000K. O:)
P.S.: the M21D just needs a 3A XHP50 driver with a small side switch mod to use the NV4B35AM.