We are working through the same issue. Too much movement in a longer travel trailer. Thanks for the suggestions so far - looks like I have a few more things to try.
Here is what we have tested so far.
Hush Pad under jack stand. It's a nice thick pad. But it didn't decrease motion significantly.
Stabilizer jack pads. These are nice. Provide some protection for the scissor jacks from the ground. But they didn't decrease motion significantly.
New chocks. Ours were old. Trying a new set. They are plastic but don't interlock with the leveling blocks. Motion increased as it is hard to secure these on the side where blocks are in place.
Super Grip Chock. These are placed between the wheels similar to an X Chock. This did reduce some of the motion and we are happy with the improvement. As others have mentioned, we use these in conjunction with regular chocks.