how to permanently preserver food, doesn't have to be edible?!

Lucky Star fan? XD Anyway, you know how gift shops encase scorpions and stuff into see-through plastic squares? Try looking into that. I'm sure there is someone who can do that for you.
Or find out which food places have the fake sample of food displayed, talk to a manager and talk to that providing company.

I would find a source for liquid nitrogen (high school or college science departments) and dip it in, then have it encased in resin. The liquid nitrogen will instantly freeze-dry it and that will keep it for a long time, but encasing it in a block of resin will seal out all air and make it last a lot longer.

There's only one way I could find, and it's bound to be terribly expensive if you could even find somebody to do it. It's a process developed by Gunther van Hagens to plasticize human bodies for exhibition. I don't even know what it's called.