Check out these dash jewels.  Fits on the 4 adjustment knobs and the 4 open/close knobs by simply sliding them over the knob and tightening with a set screw (supplied). Sold in sets of 2.  Order 2 sets for one jewel per dash vent.  Order 4 sets for the 8-piece price of $36.00. Please note,  these fit the center air control knob on all 2001-2005 PT Cruisers and they fit the lower knobs on most early Cruisers.  Fitting these dash jewels to the lower air control knob on many later model PT's may require removing the knob and shaving the outer rim of the knob a bit to allow it to fit.