I'll google Little Crafty Bugs. Shipping is from the US is probably going to cost more than the actual foam (If they are in the US) but I have really missed having the 3mm. Could you post again when you get it, to say if it is the right stuff?
Found Little Crafty Bugs, in the UK. But all I can see there is craft foam, which is firm, can be bent but is not soft and stretchy. Hope you do get the soft urethane foam.
ps it was the wrong foam, returned it! onto the bandage tomorrow probably....
Oh. Sorry to hear it.
It is possible to shave a thin sheet of foam off a bigger block sometimes, with a bandsaw or electric carving knife.
I tried splitting a 6mm sheet on the bandsaw, but it was not firm enough to stay in shape, both sides squished up and were pulled down the gap in the saw table. At least one side of the cut needs to be much thicker and self supporting, and you can sort of pull the thin side away with one hand as you cut through. 3" or 4" (75 - 100mm) foam seems to work best.
Foam places and upholsterers usually have a special foam cutter that looks like a handheld jigsaw only it has 2 blades moving in opposite directions like the carving knives, only with finer serrations. They do work better, but the carving knives are much cheaper and do work ok when they are sharp. I might look for one online myself.