If you mean the grey cloth on the inserts try an auto upholstry shop, there is a big one in Welshpool (can't think of the name) or go to an auto trimmer & see if they have any hood lining, pretty much the same stuff, I had to get a Recaro partially re covered years ago & that was the closest thing we could find to use.
Pretty sure it's got a thicker backing foam too.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.