Al, If you have a '36 carburetor it will have a round plunger shaft with nut, washer, lock washer holding the leather. If you have a later replacement like a 569S it will have a rectangular plunger shaft and non-removable leather. Contact Dean Echols who should have a replacement.
If your problem is the leather is hard and shriveled so it does not contact the sides of the tube but otherwise not damaged you can try to soak it in light oil, neetsfoot oil or ATF. The oil will swell dry leather and make it more flexible.