You might try Steele Rubber Products. I used to shop there for weatherstripping for my 64 Cutlass but they do have over 300 extrusions not specific to any car. I just went to their site and looked at those extrusions. There might be something that would work.
You could also buy the part from a junk yard and even if its damaged, you can patch it together using surgical tubing and RTV. Just patch it in an area where it wont see any abuse, like in the front of the door area. Although most autowreckers are pretty greedy and it might be cheaper just to go get new from the dealer.
I've had good luck repairing weatherstripping tears by using 3M Weatherstrip adhesive. I realize the stuff is meant to hold weatherstripping on to the car, but it's a tenacious adhesive and works well to glue torn pieces back together again. I've used it on several spots on my liftgate weatherstrip where I've dragged cargo over the rubber and torn it. Try to keep it off your hands and clothes, though!