@candidough47 - bed risers come in sets of four, but you need just two for under the legs/casters at the top of your bed.
https://www.amazon.com/s?k=Bed+risers&i=kitchen-intl-ship&crid=21OZSQOZF9PTO&sprefix=bed+risers%2Ckitchen-intl-ship%2C87&ref=nb_sb_noss_2

My wedge has never flattened and I have had it for years. Mine goes on top of the mattress. There are also inflatable wedges you can take on vacation. I got all my info from Johns Hopkins.