where to get OEM transmission pan gasket '98 3.0L

my 98 windstar 3.0 originally had a rigid transmission pan gasket (that is it didn't bend, fold etc). I assumed this was no big deal so I threw it out and replaced it with a junky aftermarket gasket that came with the kit. since then I can't find the original gasket type anywhere. my Ford dealer sells a cork flexible gasket. NAPA, Autozone etc are no help. Any ideas on where to purchase would be greatly appreciated.

There's nothing wrong with either a cord or neoprene pan gasket. Most common mistake is overtightening the bolts. That cracks the cork and then it leaks.