The Reissue head will work on the vintage U67 with only a slight modification of the mic's top portion required:
You already mentioned the seventh (ground) pin on the U67 Reissue (same head as used on the current U87Ai). You can leave that pin in place, and there are two ways to achieve connecting the seven pin head to its six pin counterpart on the mic amp:
1. Remove the plastic lid covering the high-impedance components embedded in the top of the mic amp. This will reveal a pre-positioned dummy hole exactly where the seventh pin will fit.
2. My preference, as it better protects the high-impedance components from premature contamination: leave the lid in place, and drill a hole through it on the exact position of the seventh pin. It will correspond with the pre-drilled dummy hole mentioned in #1.
Regarding broken switch nipples on your original U67: You are out of luck for a cheap solution. That switch design is three generations old, and no parts are available anymore. You would have to order a complete U87Ai/U67 Reissue head assembly.
I restore broken actuator nipples with, depending on the era, clear or white plastic rods of the same diameter, insert and glue them into the pre-drilled actuator position where the original nipple broke off, and finish the surface of the new nipple's ends to a smooth semi-round, as on the originals. With a bit of practice, the result is virtually indistinguishable from the original!