Alternative to foil wrapping a P60 drop-in (thermal silicone)

Wow this so expensive, compared to cutting up a pop can which costs me nix.

Rez, if you have a Hobby Lobby anywhere nearby, pick up 40 gauge copper sheets in various sizes for $3.99 up to $11.99. Stuff works great, cuts with a scissors:

Man thanks! Hobby lobby rox. I got a 5 mil 12"x30" for $13 shipped. They had a 40% off coupon right on their main page lol.

Ive had no joy local, over the next few weeks i might pick some up from there

Man, this stuff is sharp. I recommend wearing gloves if working with the 5 mil roll.

Copper sheet is carried by the larger bearing shops here. We use it to shim end float in shafts running taper roller bearings. It comes in different thicknesses.

I get thermal interface sheet material samples at work, to prototype thermal designs. That putty-sheet stuff the OP posted ONLY works in very thin layers. Its made to be used to compress and bridge thin air gaps between heat sources and flat heatsinks. If the air gap is large enough, its effectiveness is only marginal.