take an image with clonezilla of only the used space

I have a USB stick that contains two partitions, sda1 and sda2. I want to take an image of this stick so that I can clone onto other USBs. The USB size is 128GB. but both partitions are less than 10GB. I want to take the image so that I can clone it on any USB that is larger than 10GB. but no matter how I try, beginner or expert mode. I cant find a way to do so. It always makes the image size 124GB ( the file size of the image is small, but the image itself seems to require 124GB to work). How can I do this?