Thick rubber mats (stable/garage) (Ipswich, IP4)

We have a number of pallets that need to be moved across a few metres of reasonably solid, but not completely level gravel. Does anyone have any old rubber mats you no longer need? I'm thinking that old stable mats / garage mats / grass protection mats, that sort of thing (say ~10mm thick) might help us move the pallets without the wheels spinning in the gravel. Thank you.