Unobtainium?

Nope – SRM did power meters to fit octalink BBs. Come up on eBay occasionally.

Creaktastic 🙁

Plus one – he said Octalink, not ISIS. I’ve run Shimano 5500 Octalink BBs for years/1000s of all-weather miles without a creak.

Would it not be easier to just change the BB?

SRM. There’s a track one on the bay now. Track BCD is 140 so ring choice might be challenging. But yes SRM

Personally, I’d go pedal or swap BB

Stages do a Dura ace 7710, LH arm in Octalink flavour I think, obviously intended for track bikes but should work well enough…

Don’t forget that there are 2 octolink spline widths .

Not sure which the track used

Why you’d buy a 2-300 pound arm for a dead standard I’m no sure.

You can get power meters built into pedals rather than crank arms (Garmin Vector etc.). I don’t know how they compare to crank arm units but this might be a better option as it’ll be transferable to new crank sets when/if you upgrade.