I've been to IKEA, and I've been shopping!
I did a quick search on here for Diamond Plate, and found 22 mentions of it, but no mention of this, so apologies if it has been shown before.
IKEA call it FINFÖRDELA. For just £1, yes, one Great British Pound Sterling, you get 2, count them, sheets of Diamond Plate, 28cm x 36cm, 11" x 14¼". These are turquoise/cyan, and dark grey(gray). They are sold as food chopping boards, and are a similar hard, but flexible material to 'Self Healing' cutting mats, and at that 'throwaway price, could be used as such if they fail as Diamond Plate The diamonds are approximately 1mm x 2mm, on a 1.5mm x 3mm spacing. Boards are 1.2mm thick, smooth finish on the reverse side. The diamonds are raised from the surface, and I think this material might 'resist' resin, so could be used to take a mould (mold - for our friends in the U.S.) from.
Happy Modelling - oh, and a Happy New Year, too.