The original thick gaskets are still available from Cub Cadet.
I just got a couple of 'em last month.

I had some cork gasket material laying around and used that not a thick gasket but the carb tightened up fine I'm sure it'll work the same

FWIW:
Cork tends to be more compressible than treated paper, so you might want to
check the tightness as it compresses over time. :bigthink: