The blue pad was originally attached with WMS part number 04-10253-1, which is an inverted version of the one used in RFM, MB, NBAFB and one other game I think. I've never seen one for sale and most games I've seen in the wild (mine included) either has no rubber pad there at all or it's been just screwed on there which leaves a screw head and / or nut exposed to ball strikes. Of course no rubber pad leaves the end of the ball guide exposed to direct ball strikes.

I used one of the Stern blue nubs of death, not sure of the part number but I think it's in the link ForceFlow mentioned above. I then had the metal piece made by my nephew who works at a metal fabrication place based off dimensions someone else sent me from theirs. I thought about having him make more and probably could if someone really needs one and PinBits doesn't have any more.

Aniraf was able to get not one, but two of them from Pinbits about one year ago by calling them (the first one broke and they sent him another one), so maybe try calling them?? If not he is also the one who gave me all the measurements for the part I had fabricated.