Adhesive Tape on Evaporator Core?

I'm changing a bad heater core and evaporator while converting to R134 and can't seem to find any of the foam adhesive tape for the evaportor. Called Ford and they don't sell. They buy it from O'Reilley. Went there and they don't have it either. At least not to sell over the counter. Can anybody tell me where to get this stuff?

Thanks
Mike