Do you mean foldable as in hold a crease, or flexible?
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Is there A QDS batphone/hotline? I bet they see all kinds of materials and would share information with you. I would love it if there were a staff resource like this. If all else fails, Ben keeps saying we can email him (according to him he is the batphone), and he IS a designer. He would probably LOVE to get a design question instead of a people or company management question :)

Foldable as in hold a crease, like folding cardboard

Did you walk the aisles of Lowes? I needed something similar and they have sheets of aluminum. That will hold a crease. You may find some other material you can take out of context and use it for your project. :)

Q had one time mentioned this site (that has a ton of innovative materials) https://www.inventables.com/

Thanks for the ideas! that inventables site is pretty interesting. I still haven't found exactly what I'm looking for, but I think I'll try this silicone mat from Amazon and see if I can fold it around some shapes to get what I need.
I hate pimping, so don't click if you don't want to, but the second picture on this idea is where I'm currently at with the cardboard, but I need something more durable. The good news is that regardless of what Quirky does with the idea, it is actually working to adjust my kid's habits so I'm moving forward with trying to make a better one for our daily use.
I'm also wondering how laminating poster board and folding it might work. Anyone know how lamination holds up when folded?

I'm not sure about laminating poster board. It usually tends to look bad when creased. It could possibly work and cheap enough to try. I think your best bet is the silicone mat or a rubber bath mat. Good luck! Your rendering is quite good.

Thank you stazy, I think I'll give the silicone mat a try. I might roll it around some PVC on the ends... sort of like an upside down space bar. Not sure how to attach it yet- glue seems like it doesn't work well on silicone. I might try sewing it, or make some holes and use twist ties. I'll update the post as it moves forward.

I like ur proto just fine as is! :)

Not sure if you have discounted it already but correx is pretty much a polyprop drop-in for cardboard. Dark colours tend to 'bleach out' at the folds but white always looks crisp.
Silicone is very difficult to get anything to stick and there are many different formulations.
Laminating would only be viable in the dishwasher if you go beyond the edges and don't trim.
I would imagine low volume vac-forming might be the next step up from folded board?

Great idea! I haven't heard of correx before, but I did a little searching and it is pretty much corrugated plastic, so I can fold it like my cardboard prototype, but have it be easy to clean. What a great idea! glad I posted here. Thanks simplyinclined!
And thanks DFQ on the prototype - I like how the shape is working, but cleanup of the cardboard is difficult. A few days of dripped cereal and milk and PB&J and they are about ready for the trash.

Clear contact sticky liners used to line cabinet shelfs to make ur idea waterproof?
Or what about a scroll like look? The kids can unscroll and it locks into place?

Melamine board, you can find it at Home depot for 15-20 per 4'x8' sheet and if you score it with a box cutter, it will snap clean

Like simply said, it Sounds like a thin sheet of polypropylene plastic may work for this - a foldable, waterproof material. If you just need to fold it to make a fixed shape, a PVC material like sintra can be heated and folded to whatever shape and when cooled will be a hard plastic. You'll need to change the surface finish or add tacky materials if you want it less slippery

I want to thank everyone again for the great materials suggestions. I ended up ordering some 20x30 Plasticor corrugated plastic sheets from buy.com. These worked great! I was able to fold them using the same shape as the cardboard with some minor adjustments. Then hot glue held the forms in place. These new placemats are sturdy, easy to clean, and they look better than the cardboard. As a bonus the kids love to color on them with their washable crayons, and change out the designs every few days. You can see the results here. Thanks again for all the great suggestions!

Glad it worked out for you Michael. Good luck with the submission!