While you can get closed cell foam from foam retailers it can work out quite expensive.
Interlocking foam floor tiles are available from hardware stores advertised for kids play areas – they are inexpensive and relatively thick but firm enough not to compress with use, unlike typical exercise mats. They usually come in packs of around $10 for 4.
– Cut off the interlocking tabs
– Cut them in half to provide enough padding to cover the tramp and over the side facing the ama.
– Use cable ties to hold them in place (don’t use glue because they will need replacing in the future and removing old glue is hard).