i've got a stock header with a 2" collector but the flange on my aftermarket cat is too big for the stock 2" ID donut gasket that is 1/2" wide, so 2-1/2" OD.

Has anyone else run into this? Can you get a thicker donut gasket with a 2" ID? I called a few local parts places and they said they can't find anything for me unless i have a specific application.

Is this something a muffler or exhaust shop might carry on hand or will i be have to cut the flange off the cat and weld on a smaller flange?