There are many types of bolsters that can support a hyperbaric chamber from rolling over. Some are on wooden platforms, some have a foam support (make sure you get the type that doesn't offgass), and some have inflatable bolsters. I personally like the wooden supports.
Note: if you don't want the bolsters and are going to be putting the hyperbaric chamber next to a couch and a heavy chair or in between two things that will prevent if from rolling, make sure it will support the chamber.
With the wooden bolster that is raised it acts as a heat sync that allows heat to escape the bottom of the chamber floor. Many people complain when they sweat and lay in a puddle of sweat. A cooler can definitely help with this but having it raised off the floor takes away a few degrees as well. Also, if adding a vibro accoustic system to the bottom of the chamber, having the wooden platform raised up allows it to absorb into the chamber and not as much into the floor. (I use the Subpac S2 inside the chamber unless using the sound mat.
If buying the inflatable bolsters they do have a plastic smell to them at first. The foam has the least smell but the wooden bolster has none. They really don't like me to tell people this but if you get a chamber from one company you like but they don't have the bolster you want, you can see if they will sell you the chamber without the bolster so you can buy a different one. Sometimes they let people do this and other times, depending on which salesperson you are talking to, they want to make a chamber sale and might not let you buy it. They have caught onto this by now and know what people are trying to do when they buy just a bolster and not a chamber.
I do have access to different types of bolsters when people want to switch them out or don't need their bolsters anymore.