You can use anything that is metal or heat resistant that fits in the pressure cooker and provides support for whatever it is you are cooking. You can even use a scrunched-up piece of tin foil as a trivet.
Also, can you pressure cook meat wrapped in foil?
Almost any food which can be cooked in steam or water-based liquids can be cooked in a pressure cooker. Foil-wrapped meat analogues that are typically baked or steamed can also be cooked in a pressure cooker, but different rules apply. … At this pressure, water boils at 250°F (121°C).