I've had quite a few PMs regarding missing parts, which prompted me to start a list.
The following parts are currently not available from GM as of the post date. There may be other parts not listed. Feel free to add any other parts you can identify to this thread and I'll try to keep it updated.
Note: SMC has some obscure parts for sale. Sorry for the ugliness of the list. All column spacing between the parts and part numbers vanished when posted.
CC
Part Name -- Part Number
Left HUD Dimmer Switch Assembly ................10350594
Driver’s Side Headlight Assy ..........................20779745
Seat Frame, Right ........................................88994351
Lower Seat Cover, Left, Ebony .......................88991575
Lower Seat Cover, Right, Ebony .................... 88991577
Lower Seat Cover, Right, Shale ......................88991576
Passenger Side Seat Cushion ........................ 88898577
Driver Seat Back Pad ....................................88898497
Passenger Seat Back Pad, Center, Ebony .........88963533
Tail Lamp Assembly, Right .............................20756026
Tail Light Assembly, Left ................................20756025
Front Tonneau, Driver Side Panel, Shale .......... 88956628
DSCC Sensor (2004) ......................................10349974
Door Trim Panel, Left, Ebony/Shale ..................10333943
Seat Speaker Grill Right, Shale ........................88898588
Seat Speaker Grill Left, Shale ..........................88898588
Seat Back Speaker Grill, Shale ........................ 88898588
Fuel Tank Level Sensor, Left ........................... 10310028
HUD (2004-2005)
Outer Hinge Pillar, Left ....................................10399137
Outer Hinge Pillar, Right ..................................10399136
(Door) Lower Hinge Roller, Left .........................25965626
(Door) Lower Hinge Roller, Right .......................25965626
Grille, Grey ....................................................10349914
Instrument Panel, Shale (Dash) ........................15913737
Knee Bolster, Shale .........................................10315797
Lower Insulator, Shale (Under Stg Wheel) ..........10372870
Cluster Trim, Shale, Left ..................................10343571
Armrest, Right, Shale ......................................10351112
Armrest, Left, Shale ........................................10340191
Armrest Pad, Right, Shale ................................10340191
Door Trim Molding, Left ...................................10334469
Door Trim Molding, Right ................................ 10334470
Door Upper Trim, Shale, Left ........................... 10334527
Door Upper Trim Retainer, Right ...................... 10357837
Door Upper Trim Seal Strip, Left, Shale ..............10334532
Door Upper Trim Seal Strip, Right, Shale ........... 10334532
Door Trim Panel, Left, Shale .............................15259343
Door Insert Panel, Left, Shale ...........................15277527
Door Insert Panel, Right, Shale .........................15277522
Door Map Pocket, Left, Shale ............................10320934
Door Speaker Grille, Right, Shale ......................10320911
Back Panel Trim, Shale, (Waterfall) .................. 15232021
Roll Bar Cover, Left, Shale ...............................10321506
Roll Bar Cover, Right, Shale ............................ 10319784
(URPA) Indicator, Bezel, Shale ..........................10344044
(Trunk) Side Trim, Right ..................................25979695
Windshield Header Trim, Shale ........................ 10352597
Windshield Pillar Trim, Right, Shale .................. 21994518
Vent Grille, Windshield Pillar, Right, Shale ......... 10347233
Sunshade, Right, Shale ................................... 10334541