The pads are available as a part but when I tried to order these in January this year were back order till Feb/March The cost for a 300 gd was £20 +VAT so about £ 23.50 all told.UK price.
The material I would suggest promotes water retention and therefore rot and steam, if its diesel ingnore as the temperature aint going to be rocket levels.
For the petrol engines it depends how much room you have over the tank if its tight a piece of shaped alloy plate may be better and made into sandwich of glassfibre cloth to make a thin but firm pad.
If there is plenty of room and you can lift the pipe as high as possible straight air cooling.
The biggest problem will be getting the material which I believe is self adhesive to stick to a less than smooth surface. As in otherposts Tigerseal adhesive is ok but remember that both the rubber of the insulation material and any glue are inflamable,
although the base material is glass fibre strand reinforced.
Dave