SRM just announced X-Power flat pedals for dirt.
As an update, my x-powers continue to work well after the round trip to Colorado. Am a happy customer again. Battery life seems solid and the garmin 530 gives an alert with plenty of time remaining to complete a couple 2 hours rides.
I’ve not bothered to reference the power to my road SRm units but the readings roughly match what I expect based on terrain, RPE and how hard I’m pushing. Dirt power files are so different from road or trainer that I’m keeping mtn and road data separate for now.