What alternatives to EVA foam are there that are not made of plastic?

I plan on getting into cosplay, and I know that for a lot of work, EVA foam is used. However I was wondering if there is a non-plastic alternative that has some of the same qualities (mainly being stiff and able to hold its shape even when standing straight up). I’ve heard of the company Bloom that uses algae in their EVA foam production, but they don’t sell sheets online, so I’m assuming they only sell wholesale/to companies.

Luckily the cosplay I’m hoping to make soon doesn’t need a lot (if any) of this foam, but it would be nice to know for the future! =D