So it sits in that little groove around the outside edge, not down in the bowl?
I wish I could see the actual piece. I know - probably everybody knows what it looks like but me...lol.
I ask because I have seen repair kits on eBay and other places for $20 - $25 dollars. If it's the gasket looking part, it may be as simple as locating the correct size/shape for your existing carb, then you could possibly shoot off an email and have that part only (rather than an entire repair kit) shipped to ya for 10 bucks or less. Could prove cheaper and easier than cutting or fitting your own.