Put this under the mattress
If you like the size of what you have, you can use a rug stabilizer. Here’s one at amazon, but you can find these everywhere https://www.amazon.com/DoubleCheck-Products-Extra-Strong-Padding/dp/B01HSEP8ES/ref=asc_df_B01HSEP8ES/?tag=hyprod-20&linkCode=df0&hvadid=191929238300&hvpos=&hvnetw=g&hvrand=17336208528564463935&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031019&hvtargid=pla-302196426408&psc=1
Try some of that stuff that people put under rugs to stop them from slipping. You can cut it to fit the stand and it should work.