I have a couple of CF poles for mids.
One is from Ruta Locura. It's narrow in diameter, maybe only a little thicker than the upper section of a trekking pole, but the thickness of the wall is pretty substantial. It collapses into two sections and has a third telescoping twist lock section that nests into one of the other sections. I had it custom made to be able to do double duty for both a standard-sized mid and the (lower height) center pole on a trailstar.
I think when I later bought a duomid (used) it ended up coming with a CF pole from Seek Outside. It's a wider diameter construction (a little larger than the aluminum pole that the SL3 comes with) but a thinner guage. It collapses into three sections and has a fourth section that is adjustable to various pre-set heights (just like the stock SL 3 pole).
Both have worked well so far and proven plenty strong enough. The Ruta Locura pole is a little lighter and packs down smaller, but the twist lock isn't as fool proof as the adjustment mechanism on the Seek Outside pole.