I kinda wish I bought some spares too. I just have the one, myself. Don't know who or why or how they were convinced to switch over to the metal ones, but it kinda sucks.
If you use some blue painter's tape, you can make a little ring with the sticky side facing out... think of a ring about large enough to circle a 510 & a 1/4" wide. Use that to stick the ring on to the Stealth. For bonus points, use 2 of them 180 degrees apart. They won't damage the finish & you can't lose the ring which is the biggest potential disaster you'll face with one.