How about making silicon molds from your print then casting that in a resin that is safer? I've only done very basic silicon molds, and not very well at that, but I think with some practice and the right equipment this would also allow you to make a better end product.

https://youtu.be/iRj6xzNx7P4 looks like a nice video showing the process. I'm guessing a mouth piece would need to be done in 2 parts due to the internal structure.