Keep the nipples and re-size the caps. Caps are easily and symmetrically re-sized using a small socket from a ¼'' ratchet set. Either a 5/32” or 4mm size will work.
Simply place cap on hard flat surface open side up and apply downward force with the socket. A gentle tap may be required. If the re-sized cap resists being removed from the socket gently grab it with pliers and rock it back and forth.
I modified my socket slightly with a pointed stone on a Dremel tool to provide a forcing cone of sorts.