Good news – we have you covered! There are two, similar spider-based units that are made for your crankset.
ROTOR INspider MTB Power Meter
The ROTOR INspider MTB Power Meter is a spider-based power meter that is compatible with ROTOR’s KAPIC carbon and aluminum cranksets. The ROTOR INspider MTB records data via four sets of opposing gauges. This results in a high degree of accuracy (+/- 1.5%) and also means the power meter can measure left and right leg power balance. The INspider MTB features ANT+ and Bluetooth SMART and has a USB-rechargeable battery with 350-hour battery life. The price is also very reasonable at $499.

ROTOR INspider MTB Power Meter
power2max NGeco ROTOR MTB Power Meter
The power2max NGeco ROTOR MTB Power Meter is a very similar power meter, but is made by a different company. power2max makes wonderful power meters (some of the most accurate and dependable units we sell) with features such as dual leg power measurement, ANT+/Bluetooth SMART compatibility and left/right power balance. In addition, the NGeco is accurate to +/- 2.0% in all environmental conditions and is easy to use with features such as auto-zero and accelerometer-based cadence measurement. The price is $590.

power2max NGeco ROTOR MTB Power Meter
Sigeyi AXO ROTOR MTB Power Meter
The Sigeyi AXO ROTOR MTB Power Meter is also a spider-based power meter is compatible with ROTOR direct mount splined cranksets. The Sigeyi power meter measures power from both legs, is accurate to +/- 1.0% and is lightweight at only 83 grams. In addition, it easily bolts up to your existing ROTOR crankset. Therefore, there is no need to buy new cranks or replace your bottom bracket.

Sigeyi AXO ROTOR MTB Power Meter