Thanks both for the comments.
Power Pods weren’t on my radar - interesting tech / idea. I’ll do a bit more reading up on them - although I’m not sure I like the look of it hanging down at the front of the bike.
I think the Assioma Uno probably is top of my list at the moment. I had a further read on the stages single sided power meter and it definitely won’t fit. The 4iii precision 3 may fit - but probably too tight for comfort.