I don't know if the rubber gear lever gaitors are actually manufactured by Wadhams, but I have been warned that the new ones don't last long at all. The mechanic I favour recently repaired my very torn and decrepit original gaitor with some kind of glue, and to my amazement it is holding up well!
I have seen adverts for new pattern rubber parts of (allegedly) OEM quality over on the faceache P6 club page. The company are called Coh Baines, I think. Maybe try a DeDion boot from them?
I will soon be having Wadhams front upper link bushes installed, as my purple poly bushes in that location make too many noises. I will report back if that solves the problem. I am happy with purple poly for all the other suspension bushes.