I have a lot of Celastic hanging about, and it does have a two-step process of getting wet with acetone and drying but at 1mm thick it is quite light, strong. and flexible and will hold up to autoclaves better than acrylic.
They do look like cardboard and are as rough as cardboard but are what I have a lot of.
Any ideas about suitability to use? Are folks likely to assume they are cardboard and reject them, or even reject as not making a good first impression without testing? I would hate to make a few thousand and have folk turn their nose up at them.