Someone else may have a better suggestion, But here is mine, You can just cut a few stems and they will make it, wrap them in paper towels (or not) and place in a plastic bag, no longer then they will have to be in the bag, no need for adding moisture to it, Most sedum is very hardy, my kittens have broken off a lot of stems from mine, when I find one on the ground, I just stick it in some water to root. So you should be alright to just cut a few stems and place in a bag until you get home. Just be sure as soon as you get home to get them out of the bag. They will also root in the soil.