for under the unit, just that kind of low density sheet small hole stuff, normally they use inside bags.
for around the cable entry.. like the closed cell material that they pull air con pipes thru
its called "XPE"
google "xpe foam", you can get all sorts of colours.
They do "blocks" of it which is just layers heat bonded together, then you just cut a shape under the top layer from the back, leaving the surface intact & just velcro or glue it in
http://m.pefoamroll.com/xpe-foam/xpe-foams.html