Have you seen these by oogaa? They're non-toxic silicone and seem like a great company (I perused their site) not sure where they manufacture, but it might warrant an email as their stuff is cute & affordable & they seem solid, & have won lots of awards.
For those who are also looking, I have found these USA-made options:
This is my top contender so far. It is made of polypropylene, aka #5 plastic, one of the better ones.
This could be as good or better, if I could find as much information about acrylic as I can about polypropylene.
I'd still love silicone, but country of origin is important to me.
Update: I felt I had given Ooga enough time to reply, and they did not. I will still post their reply if I ever hear from them, since I know many people make use of the Mothering archives.
Unfortunately, I found that the Constructive Eating placemats were not well-reviewed, including a problem with smearing ink, which I found alarming. I encourage anyone interested in this brand to do their own reading, as it certainly would be nice to have a USA-made product.
Next, I thought I would go with Mimi the Sardine, but it turned out that the company is out of business, with stock remnants being sold on various sites, in a limited range of patterns. This possibly would have been the best option - I was really on the fence - but I was not crazy about the few, remaining prints, and I still couldn't see what was so great about acrylic. Besides, there were no American (or any) workers left to consider, since the company was out of business.
Finally, I...bought some Chinese placemats. Yes, I. The search was driving me absolutely crazy. I ordered some silicone placemats from a company called Brinware. I would link them here, but since they are Chinese, I am going to leave that to Google.