How about some of these, or similar, old mini cotton reels.
http://www.ebay.co.uk/itm/SET-OF-4-...Air_Tools_and_Compressors&hash=item3a8058c51e
http://www.ebay.co.uk/itm/CLASSIC-M...arts_Vehicles_CarParts_SM&hash=item5ae8ff0ee4
I just used some old thick rubber under mine, then doubled it over as well.
Or even an old rubber car mat under it.
http://www.ebay.co.uk/itm/SET-OF-4-...Air_Tools_and_Compressors&hash=item3a8058c51e
http://www.ebay.co.uk/itm/CLASSIC-M...arts_Vehicles_CarParts_SM&hash=item5ae8ff0ee4
I just used some old thick rubber under mine, then doubled it over as well.
Or even an old rubber car mat under it.