Hey José,
How about that, I remembered how to make your "é". Pretty cool huh? Anyway, nope, I personally have never heard of anyone replacing just the little seals inside those extenders. I don't know if they can be replaced but, it may be worth looking into. I suppose you could dissect one of them and see what the seal looks like and then, head down to your local AutoZone or whatever's close and see if they have anything that comes close.
How's the ticker? Getting your exercise? Blanca doing fine?
Scott