For those still suggesting rubber, see post 25. That's already done.
As far as the nipples are concerned, no, the threads don't match. It took me a half hour on line to learn more about spokes and nipples than any of a dozen shops I called this morning seemed to know. 2 of them (on the opposite ends of town) said they did have 15 gauge nipples in stock, so I rode my motorcycle over 40 miles, through Phoenix traffic, in AZ heat, to find that one place had them but with the new threads, and the other didn't really have any after all.
I don't feel bad about shopping on line anymore.