you can use wet pieces of paper towel, seal them up with the buds and in a few hours the buds will rehydrate. although you will no longer be able to continue the curing process, once the bud dries out that process is over.
If you have a grow growing you can use a leaf from a plant. Just add one or two depending on the size of the leafs to your jar and let set for a day or two. Many use orange peels or a small piece of apple.......