Does anyone have any ideas as to how I can make or where I can buy them?
A Google search on “fake braces costume” produced [(scroll down to the bottom). Looks like a British site, though – not much help if you’re in the US.
Then there’s [url=http://www.toothfairyteeth.com/pages/catalogue/big_teeth_braces.html]this site,](http://www.the-joke-shop.com/showcat.asp?category=8[this site[/url) which looks US but they’re pricey ($55).
Nuts.
Double nuts.
Take the little plastic wires you use to tie freezer bags.
Strip off the plastic and you have a strong but pliable wire, bend it into the right shape and stick the ends between your teeth at the top, like you would with floss 
Or buy wire…