Made my own rear diff spacers for my 35mm raised van. I used 10mm thick aluminium plate from local scrapyard. Theres 3 bolts holding the rear differential cradle on the chassis, M12x100x1,5 in the front, this bolt is long enough for at least a 10mm spacer, the 2 rear bolts are M10x110x1,5 and these are all grade 10.9 bolts. You need to replace the rear bolts when lowering the diff, with my 10mm spacers i went for M10x125x1,5 in the back, from the dealer OEM style bolts, not that expensive, but these do not have to from the dealer. The rear spacers are 10mm thick, 85mm in diameter with a center hole of 10mm. The front spacer is 10mm thick 65mm in diameter with a 12mm center hole. Cut these with an angle grinder, 2 euros for an aluminium cutting specific disc. They are somewhat roundish, but will still perform perfect. Total costs about 30€/£25, time to make 0,5 hour.
Front bolt M12 torques to 90Nm, and then tighten 180° more. Rear M10 bolts torqued to 50Nm + 180°.