I don't believe that Cobb makes any powermeters.

I wasnt sure if something like a stages or 4iiii would make a left crank arm that would work with a cobb set up?

The Stages and 4iiii websites don't show any Cobb crank arms.

Yeah i had checked them as well. Wanted to ask on here to be sure i wasn't missing another option.

Cobb looks to have some GXP cranks. I'd bet it's just a rebadged SRAM/Trutive/Oval crank. Try someone's SRAM GXP crankarm. If it fits, any SRAM Stages GXP will work (road or mtb). Are you using a weird size?
Otherwise, you're looking at pedal, hub, or chainring solutions. Maybe also be economical to get a new Shimano 105/Ultegra crank and Stages/4iiiiiiiiiiiiii solution.

Powertap C1 ought to work, provided your Cobb crankset is 110 BCD. I’ve got a set in good condition that I could sell you.

Sent you a PM

Did you ask if you can send the left arm into 4iiii and see if they can install a gauge on the arm?

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2019 T-Rex Tri Series

Interested in your Powertap C1. Shoot me a PM with specifics. thanks