Any small bags that mount to seat post? I am looking for something similar to a saddle bag but that mounts to the seat post and not the saddle.

I have a rear mounted camera that attaches to the saddle so want a bag that I can mount lower down on the seat post. I want to keep tubes, CO2, multitool etcetera in there.

I have searched and can't find anything.

Thanks
Maybe one of Revelate Designs Jerry Can bags would work for you.  The mount on the front side of the seatpost and would leave the rear of your seat post open for your camera.  They are pretty versatile, I have used one on top of the triangle, inside the triangle and a few other places I won't mention.