Scavenger Hunt: Need a big plastic saucer...

[Kaneman]

So I'm making some paper mache shields for my son and step-son to have Spartanesque fights to the death with in the living room. I'm using garbage can lids to reinforce, and that's pretty much the perfect size...

But now I'm wanting to get in on the action. I'm trying it with chickenwire stretched over a papasan to get a close enough shape , but I don't think that's going to be strong enough. I wanna be able to knock these little bastards on their ass.

I need a plastic frame, about 3", in a saucer shape. The only thing I've found so far is a large saucer sled, which is cool, but I don't wanna drop $50 on a sheet of plastic.

Any ideas on how to make a strong 3" paper mache Spartan shield?