If you're running 914 gauges, as most are these days, the chrome bezels from the original 356 gauges will replace them perfectly. The larger bezel on the tach will take a Jager tach bezel from a Sunbeam Alpine or Triumph TR-4 I believe.
Most of the Ebayers selling gauges at auction also have broken stuff that they've picked up at flea markets and such. Contact them and ask about bezels or broken gauges. Never pay for a complete working gauge, the electrics are usually 6 volt and broken, the tach is cable drive, the fuel gauge uses a different sender and resistance, and you doubtfully have the correct oil temp sending unit to match the combo gauge, and they cost $$.
Or . . . run down to the local hobby shop and pick up a silver leafing kit and try that on the bezel. The directions are right there and it works pretty well . . . but you gotta have some patience.
The leafing kits also come in aluminum, gold, copper, and bronze I believe. The dash knobs look GREAT in gold, but are all wrong for a Porsche . . . too bad.
Hobby shops can be your best friend.
Luck,
TC