Just looked up the receipt for when my Dad bought his mini in 1960. List price ex-works £378 10/- and purchase tax an eye-watering £158 16/8
I guess the Treasury really needed the 8d
The stuff you want is called 8 micron shimstock, not occlusal indicator paper which can be up to <shudders> 200 microns thick. DOI - ex-dentist
Best wishes, John