Another part that I have found no replacement for is the foam flap at the end of the diverter door pictured below. I pulled the staples out then cut to fit a piece of felt to fit. You can get from Home Depot. IIRC the felt extended about 1.5" past the end. I reused the staples to attach it and have no leakage around the end of the metal door.
Hey - great minds think alike. I renewed the seal on the end of the defrost/floor heat valve as well. I used foam insulation and bonded it to the valve damper with adhesive cement. I can't remember why that little gap bothered me enough to go through the hassle. That was 10 years ago and it is still in place. I don't know who came up with that stupid staple idea but it wasn't the best method.
Another modification that John and I came up with - to tighten the seal between the casing and flap -was to extend the effective stroke of the actuator by relocating the valve's pin to the 2nd hole in the link.
As assembled at the factory it is in the hole closest to the motor. But if the outer hole is used, the flap acquires a quite a bit more range in the upward direction (against the defrost vent opening by spring pressure when the HEAT mode is selected). Yet there is no negative effect when the DEFROST mode is selected.
Vacuum applied:
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No vacuum to actuator:
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Original gap (using inner hole):
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Reduced gap (using outer hole):
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