If you're not concerned about originality and correctness, but are concerned about durability, this has worked for me.
I use a Dremel tool with a drill bit to smooth out the area where the break occurred. Try to leave as much of the original material as possible. Use care because you don't want to make the face plate any thinner than it already.
Find appropriate diameter steel or brass tubing (avail at hobby stores). Heat tubing until it glows red, lower tubing into plastic about 1/16 inch. Tubing must be at the same angle as the broken post. Hold in place until tubing cools.
Cut off tubing at appropriate length with a Dremel with a cut off wheel. I don't recommend pre-cutting before heating because it can be difficult to handle a short piece of very hot tubing. If using pliers to hold it, the pliers become a heat sink for the part making getting it hot and keeping that way long enough to fuse it to plastic.
Reinforce joint of plastic and metal with epoxy or JB Weld. Take car not to build it up so high it interferes with the fit of the part into the dash. Allow to set.
Get an o-ring that fits snugly on the tubing. Coat tubing with Armor-all or a silicone spray. Insert part into place and slip o-ring on post. Hole in dash may be too large for the o-ring to secure the part, in which case, a washer will need to be placed between the dash and the o-ring. I haven't recommended speed nuts because I've had problems with the torque required to use a screw on fastener sometimes breaks the tubing loose. If you're concerned about the o-ring backing off, clean the tubing and wrap with a little plastic electrial tape.
Hope this is clear enough for you to understand and is helpful. Good luck.
