Polyurethane Resins safe in frog enclosures?

[rosequoll]

I'm looking to make some custom 'ornaments' for my frog enclosure, and I'm having a heck of a time working out what resin I can use to make these with. I KNOW there's resin that's okay out there as most aquarium ornaments are made with this, as well as snake hides and bowls and all that, but I'm not sure what materials are used.

Any help would be great, thanks!