Just to close the loop on this, I was banking on the fact that Oliver may eventually be able to get more weatherstripping from Lippert, however, it seems that that still has not happened. So we tried a couple of different solutions to clean the weatherstripping before ordering the black, and lo and behold a solution of bleach and dish soap brought things nearly back to the original white. Minimal amount of scrubbing. Soaked for about 20 minutes.